Am J Physiol Heart Circ Physiol 307: H1262–H1263, 2014; doi:10.1152/ajpheart.00525.2014.
Letter to the Editor
Letter to the editor: “Why isn’t clinical experience with ouabain more widely accepted?” Hauke Fürstenwerth Freelance Consultant, Leverkusen, Germany TO THE EDITOR:
In the article “Why isn’t endogenous ouabain more widely accepted?” (2), Mordecai P. Blaustein refers to Thomas Kuhn in stating that scientists tend to ignore ideas and data that don’t fit their preconceptions and often don’t even read (or digest) articles that fall outside their “comfort zone.” Such a behavior is certainly true for many scientists engaged in research on endogenous ouabain. How else can it be explained that in the many publications on endogenous ouabain, no reference is made to the clinical experience with ouabain in the treatment of heart disease? How else can one claim, ouabain causing heart damage despite well-documented positive clinical experience in the treatment of heart disease with ouabain? How else can one neglect current reports on cardio protection induced by ouabain (12)? How else can one assert that endogenous ouabain raises blood pressure although in clinical experience a reduction of high blood pressure in patients is observed on treatment with ouabain (8, 14, 15)? In addition, ouabain reduces blood pressure in several animal species (5). How else can one claim to be surprised by an antagonistic relationship between digoxin and ouabain when ouabain has been used effectively to treat digitalis intoxication? Corresponding reports are documented as early as 1902. Recent in vitro and in vivo studies confirm this well-known clinical observation (13). Ouabain has been widely used in Europe, and especially in Germany, to treat heart failure. As early as 1904, a standardized solution of the pure substance was commercialized by E. Merck, Darmstadt and Boehringer Mannheim as “g-Strophanthin Thoms.” This ouabain solution was used both intravenously (4) and orally administered in the treatment of heart diseases. In 1909, the French physician Henri Vaquez introduced the intravenous application of ouabain (“Ouabain-Arnaud”) in France (16, 17). Some medical centers in the United States, too, have used the “French preparations” to treat heart diseases (9). The database of the German Institute for Medical Documentation and Information records more than 20 orally administered ouabain preparations that were used in Germany after 1950. In 1949 Boehringer Mannheim introduced a version of ouabain formulated as a tablet for sublingual application under the brand name Strophoral. In clinical practice, inconsistent experiences were made with the use of Strophoral, which provoked doubts about the reliability of its absorption. Pharmacological studies led to the development of improved products such as Purostrophan Dragees, Alvoral mr, and Strodival mr that all were enteric coated preparations. Strophoperm, Strophinos, and Strophocor N were oleophilic solutions for sublingual administration. With these preparations the neces-
Address for reprint requests and other correspondence: H. Fürstenwerth, Unterölbach 3A, 51381 Leverkusen, Germany (e-mail: hauke@fuerstenwerth. com). H1262
sary dosage for reliable therapeutic results were achieved at a considerably lower dosages than with Strophoral. The daily dose of Strophoral often amounted to 20 –30 mg ouabain (7); for the Purostrophan enteric-coated tablets, 2– 6 mg/day were sufficient (18). The daily dose of Strophoperm with 0.5–1 mg ouabain compared in magnitude with intravenous-administered ouabain (1). After oral and perlingual administration of ouabain preparations, serum concentrations between 0.1 and 0.9 ng/ml have been measured (3, 6). Until well into the 1970s, total absorption of a drug was considered to be the relevant criterion and not serum concentration. Today drugs such as Aliskiren, whose absorption rate is about 3%, will not be rejected just because the absorption rate is too low. Aliskiren’s therapeutic effects derive from sufficiently high serum concentrations, not from the total amount absorbed. The same is true for drugs like Nisoldipine (5%), Dabigatranetextilat (6.5%), or Ramipril (15%), which have absorption rates comparable to that of ouabain. For ouabain, absorption rates of 10% have been measured (11). Thus, contrary to textbook knowledge handed down over the decades, ouabain in appropriate galenic formulations is suitable for oral administration. In addition to the uncertainty on the identity of endogenous ouabain (10), the ignorance of the extensive literature on the clinical experience with ouabain certainly contributes to the fact that endogenous ouabain “isn’t more widely accepted.” DISCLOSURES No conflicts of interest, financial or otherwise, are declared by the author. AUTHOR CONTRIBUTIONS H.F. drafted, edited, revised, and approved final version of manuscript. REFERENCES 1. Altmann K. Beitrag zur peroralen Strophanthintherapie. Med Klin (Munich) 47: 446 –448, 1952. 2. Blaustein MP. Why isn’t endogenous ouabain more widely accepted? Am J Physiol Heart Circ Physiol 307: H635–H639, 2014. 3. Erdle HP, Schultz KD, Wetzel E, Gross F. Resorption und Ausscheidung von g-Strophanthin nach intravenöser und perlingualer Gabe. Dtsch Med Wochenschr 104: 976 –979, 1979. 4. Fleischmann P, Wjasmensky H. Über intravenöse Strophanthintherapie bei Verwendung von gratus - Strophanthinum crystallisatum Thoms. Deutsche Medizinische Wochenschrift 35: 918 –921, 1909. 5. Fürstenwerth H. On correlation and causality. Crit Care Med 41: e140 – e141, 2013. 6. Greeff K, Köhler E, Strobach H, Verspohl E. Zur Pharmakokinetic des g-Strophanthin. Verh Dtsch Ges Kreislaufforsch 40: 301–305, 1974. 7. Halhuber M, Lantscherat T, Meusburger K. Zur Strophoraltherapie. Med Klin 36: 1440 –1443, 1954. 8. Kracke R. Zur perlingualen Strophanthintherapie. Dtsch Med Wochenschr 79: 81–83, 1954. 9. Levine SA. The potency of some French digitalis preparations. Boston Med Surg J 182: 64 –66, 1920. 10. Lewis LK, Yandle TG, Hilton PJ, Jensen BP, Begg EJ, Nicholls MG. Endogenous ouabain is not ouabain. Hypertension. 2014 Jul 7. pii: HYPERTENSIONAHA.114.03919. [Epub ahead of print].
0363-6135/14 Copyright © 2014 the American Physiological Society
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Letter to the Editor LETTER TO THE EDITOR 11. Marchetti GV, Marzo A, De Ponti C, Scalvini A, Merlo L, Noseda V. Blood levels and tissue distribution of 3 H-ouabain administered per os. An experimental and clinical study. Arzneimittelforschung 21: 1399 – 1403, 1971. 12. Morgan EE, Li Z, Stebal C, Belliard A, Tennyson G, Salari B, Garlid KD, Pierre SV. Preconditioning by subinotropic doses of ouabain in the Langendorff perfused rabbit heart. J Cardiovasc Pharmacol 55: 234 –239, 2010. 13. Nesher M, Shpolansky U, Viola N, Dvela M, Buzaglo N, Cohen Ben-Ami H, Rosen H, Lichtstein D. Ouabain attenuates cardiotoxicity induced by other cardiac steroids. Br J Pharmacol 160: 346 –354, 2010.
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14. Rothmund W. Über die Entstehung der essentiellen Hypertonie. Notabene Medici 7: 22–32, 1977. 15. United States Patent Office. United States Patent 4, 020, 159, Methods of, and medications for treating cardiac disorders by using strophanthin. Filed October 8, 1974 by Herbert K. G. 16. Vaquez H, Leconte. Les injections intraveneuses de strophanthine dans le traitement de l’insuffisance cardiaque. Bull. et mem. Soc. med d’hop, Paris, xvii, 662–679, 1909. 17. Vaquez H, Lutembacher L. Ouabaine. Arch Mal Coeur 10: 197, 1917. 18. Wiesend W. Über perorale Strophanthinbehandlung, besonders beim Altersherz. Münchener medizinische Wochenschrift 98: 900 –904, 1956.
AJP-Heart Circ Physiol • doi:10.1152/ajpheart.00525.2014 • www.ajpheart.org
Am J Physiol Heart Circ Physiol 307: H1264–H1265, 2014; doi:10.1152/ajpheart.00571.2014.
Letter to the Editor
Reply to “Letter to the editor: ‘Why isn’t clinical experience with ouabain more widely accepted?’” Mordecai P. Blaustein Departments of Physiology and Medicine, University of Maryland School of Medicine, Baltimore, Maryland REPLY:
Fürstenwerth (12a) notes that my “Perspectives” on endogenous ouabain (EO) (2) 1) didn’t mention the use of ouabain as a therapeutic and antihypertensive agent (true; see last paragraph); 2) didn’t consider the view that “(EO) is not ‘ouabain’” (21) [I cited an earlier version (32) and the refutation (24); my article (2) was published online 4 days before Lewis and colleagues’ (21); see our responses to Lewis et al. (2a, 14)]; and 3) called the 1993 discovery of ouabaindigoxin antagonism (27) “a surprise,” despite the 2010 report that ouabain antagonizes acute digoxin and bufalin cardiotoxicity (31). Manunta et al. (26, 27) were, surely, the first to document that cardiotonic steroids (CTS) could antagonize one another and that all CTS do not have identical effects (e.g., ouabain, but not digoxin, causes hypertension). Thus this was “a surprise” in 1993. Nesher and colleagues (31) confirmed that ouabain and digoxin antagonize one another acutely but didn’t address the mechanism (41). The mechanism for antagonizing the chronic effects of ouabain (26, 27), not studied by Nesher, is apparently more complex (47). Fürstenwerth cites the Lewis/Hilton/Nichols group (21) regarding “uncertainty on the identity of EO.” The repeatedly verified analytical (HPLC plus mass spectroscopy, nuclear magnetic resonance, and UV) evidence that mammalian (including human) EO is, in fact, “ouabain” (13, 16 –18, 39, 42) is not mentioned, although this contradicts the Lewis et al. view (21). The latter had already been refuted twice (23, 24). Moreover, much additional, independent, but generally overlooked evidence confirms that the endogenous substance is chemically very “ouabain-like.” First, ouabain-resistant mutation of the ␣2 Na⫹ pump ouabain binding site abolishes the hypertensinogenic actions of ACTH and ouabain (10, 11, 22), proof that an EO-like ligand binds to this receptor. Second, prolonged subcutaneous administration of ouabain, but not digoxin, induces hypertension in rodents (15, 26, 44, 47). Ouabain’s effect has been replicated in numerous laboratories in the United States, Brazil, Canada, China, and Italy. Third, ouabain, but not digoxin, also increases expression of Ca2⫹ transporters, including Na⫹/Ca2⫹ exchanger-1 in arteries (47). Similar upregulation of these arterial transporters occurs in many forms of hypertension (4, 35, 36, 46). Fourth, digoxin blocks both the ouabain-induced protein upregulation (47) and hypertension (15, 26, 27). Fifth, complexation of EO with Fab fragments that bind digoxin and ouabain with high affinity (37, 38) abolishes several forms of hypertension (4), including those induced by ACTH (10), ouabain (10, 15), and high dietary salt (15). Sixth, reduced expression of ␣2 Na⫹ pumps (the EO receptors), equivalent to ␣2 Na⫹ pump inhibition by Address for reprint requests and other correspondence: M. P. Blaustein, Dept. of Physiology, Univ. of Maryland School of Medicine, 655 W. Baltimore St., Baltimore, MD 21201 (e-mail: [email protected]). H1264
nanomolar EO/ouabain, induces hypertension (5, 7, 45), whereas ␣2 overexpression lowers blood pressure (BP) (7, 34). Given these many related, consistent, and widely replicated observations, the burden is on the few groups (1, 9, 21) that have been unable to purify EO or to induce hypertension with ouabain to explain why not. Contradictory observations can’t both be correct, and negative results are not proof that EO is not ouabain. One must distinguish solid data from artifacts of experimental design and/or execution. It’s highly unlikely that EO spectra from five independent laboratories are all artifacts or that the ⬎12 laboratories that have described ouabaininduced hypertension in rodents are all wrong. Undoubtedly, EO has beneficial effects (30). Plasma EO is increased in normal pregnancy (16), and pregnant mice with ouabain-resistant ␣2 Na⫹ pumps have low BP (33). Plasma EO is also elevated during salt depletion (3, 25), and its acute and chronic vasotonic effects likely help minimize BP decline (3). Acutely, ouabain/EO can enhance cardiac and vascular (6, 20, 43) contractility. Nevertheless, acute intravenous administration of ouabain not only increases resistance to blood flow in humans (28) but, in hypertensive patients, may have devastating cerebrovascular and cardiovascular effects (19). Tests of oral ouabain clinical efficacy cited by Fürstenwerth are anecdotal. There are no controlled clinical trials and certainly none that compare efficacy to plasma ouabain level, a crucial problem, given the low and irregular absorption of oral ouabain (12). Indeed, ignorance of EO and lack of controlled trials continues to undermine all clinical studies of cardiotonic steroid efficacy [e.g., (8, 29, 40)]. Absent quality data, there is little rationale for discussing the clinical use of ouabain. DISCLOSURES No conflicts of interest, financial or otherwise, are declared by the author. AUTHOR CONTRIBUTIONS M.P.B. drafted, edited, revised, and approved final version of manuscript. REFERENCES 1. Baecher S, Kroiss M, Fassnacht M, Vogeser M. No endogenous ouabain is detectable in human plasma by ultra-sensitive UPLC-MS/MS. Clin Chim Acta 431: 87–92, 2014. 2. Blaustein MP. “Why isn’t endogenous ouabain more widely accepted?” Am J Physiol Heart Circ Physiol 307: H635–H639, 2014. 2a.Blaustein MP. Re:Re:Re: “Endogenous Ouabain is Not Ouabain” by Lewis et al. Hypertension (Online First on July 7, 2014; doi: 10.1161/ HYPERTENSIONAHA.114.03919). Epub Comment, August 25, 2014. 3. Blaustein MP, Chen L, Li M, Gao J, Hamlyn JM. Angiotensin II triggers the same pressor mechanisms in salt-sensitive hypertension and during salt depletion. Hypertension 62: A19, 2013. 4. Blaustein MP, Leenen FH, Chen L, Golovina VA, Hamlyn JM, Pallone TL, Van Huysse JW, Zhang J, Wier WG. How NaCl raises blood pressure: a new paradigm for the pathogenesis of salt-dependent hypertension. Am J Physiol Heart Circ Physiol 302: H1031–H1049, 2012. 5. Blaustein MP, Zhang J, Chen L, Song H, Raina H, Kinsey SP, Izuka M, Iwamoto T, Kotlikoff MI, Lingrel JB, Philipson KD, Wier WG, Hamlyn JM. The pump, the exchanger, and endogenous ouabain: signal-
0363-6135/14 Copyright © 2014 the American Physiological Society
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Letter to the Editor LETTER TO THE EDITOR ing mechanisms that link salt retention to hypertension. Hypertension 53: 291–298, 2009. 6. Bova S, Blaustein MP, Ludens JH, Harris DW, DuCharme DW, Hamlyn JM. Effects of an endogenous ouabainlike compound on heart and aorta. Hypertension 17: 944 –950, 1991. 7. Chen L, Song H, Kotlikoff MI, Lee J, Pritchard TJ, Paul RJ, Li M, Blaustein MP. Blood pressure correlates directly with the expression level of high ouabain affinity alpha-2 Na⫹ pumps in arterial smooth muscle. Hypertension 62: A19, 2013. 8. Digitalis Investigative Group. The effect of digoxin on mortality and morbidity in patients with heart failure. N Engl J Med 336: 525–533, 1997. 9. Doris PA, Jenkins LA, Stocco DM. Is ouabain an authentic endogenous mammalian substance derived from the adrenal? Hypertension 23: 632– 638, 1994. 10. Dostanic-Larson I, Van Huysse JW, Lorenz JN, Lingrel JB. The highly conserved cardiac glycoside binding site of Na,K-ATPase plays a role in blood pressure regulation. Proc Natl Acad Sci USA 102: 15845–15850, 2005. 11. Dostanic I, Paul RJ, Lorenz JN, Theriault S, Van Huysse JW, Lingrel JB. The ␣2-isoform of Na-K-ATPase mediates ouabain-induced hypertension in mice and increased vascular contractility in vitro. Am J Physiol Heart Circ Physiol 288: H477–H485, 2005. 12. Erdle HP, Schultz KD, Wetzel E, Gross F. Absorption and excretion of g-strophanthin after intravenous or sublingual administration [Author’s translation]. Dtsch Med Wochenschr 104: 976 –979, 1979. 12a.Fürstenwerth H. Letter to the editor: “Why isn’t clinical experience with ouabain more widely accepted?” Am J Physiol Heart Circ Physiol 307; doi:10.1152/ajpheart.00525.2014. 13. Hamlyn JM, Blaustein MP, Bova S, DuCharme DW, Harris DW, Mandel F, Mathews WR, Ludens JH. Identification and characterization of a ouabain-like compound from human plasma. Proc Natl Acad Sci USA 88: 6259 –6263, 1991. 14. Hamlyn JM, Manunta P, Blaustein MP. “Endogenous Ouabain is Not Ouabain” by Lewis et al. (Online First on July 7, 2014; doi:10.1161/ HYPERTENSIONAHA.114.03919). Hypertension Epub Comment, July 28, 2014. 15. Huang BS, Kudlac M, Kumarathasan R, Leenen FH. Digoxin prevents ouabain and high salt intake-induced hypertension in rats with sinoaortic denervation. Hypertension 34: 733–738, 1999. 16. Jacobs BE, Liu Y, Pulina MV, Golovina VA, Hamlyn JM. Normal pregnancy: mechanisms underlying the paradox of a ouabain-resistant state with elevated endogenous ouabain, suppressed arterial sodium calcium exchange, and low blood pressure. Am J Physiol Heart Circ Physiol 302: H1317–H1329, 2012. 17. Kawamura A, Guo J, Itagaki Y, Bell C, Wang Y, Haupert GT, Jr., Magil S, Gallagher RT, Berova N, Nakanishi K. On the structure of endogenous ouabain. Proc Natl Acad Sci USA 96: 6654 –6659, 1999. 18. Komiyama Y, Nishimura N, Dong XH, Hirose S, Kosaka C, Masaki H, Masuda M, Takahashi H. Liquid chromatography mass spectrometric analysis of ouabainlike factor in biological fluid. Hypertens Res 23, Suppl: S21–S27, 2000. 19. Kumar R, Yankopoulos NA, Abelmann WH. Ouabain-induced hypertension in a patient with decompensated hypertensive heart disease. Chest 63: 105–108, 1973. 20. Lee CO, Kang DH, Sokol JH, Lee KS. Relation between intracellular Na ion activity and tension of sheep cardiac Purkinje fibers exposed to dihydro-ouabain. Biophys J 29: 315–330, 1980. 21. Lewis LK, Yandle TG, Hilton PJ, Jensen BP, Begg EJ, Nicholls MG. Endogenous ouabain is not ouabain. Hypertension 2014 Jul 7. pii: doi: 10.1161/HYPERTENSIONAHA.114.03919. [Epub ahead of print]. 22. Lorenz JN, Loreaux EL, Dostanic-Larson I, Lasko V, Schnetzer JR, Paul RJ, Lingrel JB. ACTH-induced hypertension is dependent on the ouabain-binding site of the ␣2-Na⫹-K⫹-ATPase subunit. Am J Physiol Heart Circ Physiol 295: H273–H280, 2008. 23. Manunta P, Ferrandi M. Different effects of marinobufagenin and endogenous ouabain. J Hypertens 22: 257–259, 2004. 24. Manunta P, Ferrandi M, Bianchi G, Hamlyn JM. Endogenous ouabain in cardiovascular function and disease. J Hypertens 27: 9 –18, 2009. 25. Manunta P, Hamilton BP, Hamlyn JM. Salt intake and depletion increase circulating levels of endogenous ouabain in normal men. Am J Physiol Regul Integr Comp Physiol 290: R553–R559, 2006. 26. Manunta P, Hamilton J, Rogowski AC, Hamilton BP, Hamlyn JM. Chronic hypertension induced by ouabain but not digoxin in the rat:
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antihypertensive effect of digoxin and digitoxin. Hypertens Res 23, Suppl: S77–S85, 2000. Manunta P, Tyzack J, Hamilton BP, Hamlyn JM. Augmentation and antagonism of ouabain-induced hypertension. Hypertension 22: 432, 1993. Mason DT, Braunwald E. Studies on digitalis. X effects of ouabain on forearm vascular resistance and venous tone in normal subjects and in patients in heart failure. J Clin Invest 43: 532–543, 1964. Mulder BA, Van Veldhuisen DJ, Crijns HJ, Tijssen JG, Hillege HL, Alings M, Rienstra M, Van den Berg MP, Van Gelder IC, Investigators RI. Digoxin in patients with permanent atrial fibrillation: data from the RACE II study. Heart Rhythm 11: 1543–1550, 2014. Nesher M, Dvela M, Igbokwe VU, Rosen H, Lichtstein D. Physiological roles of endogenous ouabain in normal rats. Am J Physiol Heart Circ Physiol 297: H2026 –H2034, 2009. Nesher M, Shpolansky U, Viola N, Dvela M, Buzaglo N, Ben-Ami HC, Rosen H, Lichtstein D. Ouabain attenuates cardiotoxicity induced by other cardiac steroids. Br J Pharmacol 160: 346 –354, 2010. Nicholls MG, Lewis LK, Yandle TG, Lord G, McKinnon W, Hilton PJ. Ouabain, a circulating hormone secreted by the adrenals, is pivotal in cardiovascular disease. Fact or fantasy? J Hypertens 27: 3–8, 2009. Oshiro N, Dostanic-Larson I, Neumann JC, Lingrel JB. The ouabainbinding site of the ␣2 isoform of Na,K-ATPase plays a role in blood pressure regulation during pregnancy. Am J Hypertens 23: 1279–1285, 2010. Pritchard TJ, Bullard DP, Lynch RM, Lorenz JN, Paul RJ. Transgenic Mice Expressing Na⫹-K⫹ ATPase in smooth muscle decreases blood pressure. Am J Physiol Heart Circ Physiol 293: H1172–H1182, 2007. Pulina MV, Zulian A, Baryshnikov SG, Linde CI, Karashima E, Hamlyn JM, Ferrari P, Blaustein MP, Golovina VA. Cross talk between plasma membrane Na⫹/Ca 2⫹ exchanger-1 and TRPC/Orai-containing channels: key players in arterial hypertension. Adv Exp Med Biol 961: 365–374, 2013. Pulina MV, Zulian A, Berra-Romani R, Beskina O, Mazzocco-Spezzia A, Baryshnikov SG, Papparella I, Hamlyn JM, Blaustein MP, Golovina VA. Upregulation of Na⫹ and Ca2⫹ transporters in arterial smooth muscle from ouabain-induced hypertensive rats. Am J Physiol Heart Circ Physiol 298: H263–H274, 2010. Pullen MA, Brooks DP, Edwards RM. Characterization of the neutralizing activity of digoxin-specific Fab toward ouabain-like steroids. J Pharmacol Exp Ther 310: 319 –325, 2004. Pullen MA, Harpel MR, Danoff TM, Brooks DP. Comparison of non-digitalis binding properties of digoxin-specific Fabs using direct binding methods. J Immunol Methods 336: 235–241, 2008. Schneider R, Wray V, Nimtz M, Lehmann WD, Kirch U, Antolovic R, Schoner W. Bovine adrenals contain, in addition to ouabain, a second inhibitor of the sodium pump. J Biol Chem 273: 784 –792, 1998. Shah M, Avgil Tsadok M, Jackevicius CA, Essebag V, Behlouli H, Pilote L. Relation of digoxin use in atrial fibrillation and the risk of all-cause mortality in patients ⬎/⫽65 years of age with versus without heart failure. Am J Cardiol 114: 401–406, 2014. Song H, Karashima E, Hamlyn JM, Blaustein MP. Ouabain-digoxin antagonism in rat arteries and neurones. J Physiol 592: 941–969, 2014. Tamura M, Harris TM, Phillips D, Blair IA, Wang YF, Hellerqvist CG, Lam SK, Inagami T. Identification of two cardiac glycosides as Na(⫹)-pump inhibitors in rat urine and diet. J Biol Chem 269: 11972– 11979, 1994. Weiss DN, Podberesky DJ, Heidrich J, Blaustein MP. Nanomolar ouabain augments caffeine-evoked contractions in rat arteries. Am J Physiol Cell Physiol 265: C1443–C1448, 1993. Yuan CM, Manunta P, Hamlyn JM, Chen S, Bohen E, Yeun J, Haddy FJ, Pamnani MB. Long-term ouabain administration produces hypertension in rats. Hypertension 22: 178 –187, 1993. Zhang J, Lee MY, Cavalli M, Chen L, Berra-Romani R, Balke CW, Bianchi G, Ferrari P, Hamlyn JM, Iwamoto T, Lingrel JB, Matteson DR, Wier WG, Blaustein MP. Sodium pump ␣2 subunits control myogenic tone and blood pressure in mice. J Physiol 569: 243–256, 2005. Zulian A, Baryshnikov SG, Linde CI, Hamlyn JM, Ferrari P, Golovina VA. Upregulation of Na⫹/Ca2⫹ exchanger and TRPC6 contributes to abnormal Ca2⫹ homeostasis in arterial smooth muscle cells from Milan hypertensive rats. Am J Physiol Heart Circ Physiol 299: H624–H633, 2010. Zulian A, Linde CI, Pulina MV, Baryshnikov SG, Papparella I, Hamlyn JM, Golovina VA. Activation of c-SRC underlies the differential effects of ouabain and digoxin on Ca2⫹ signaling in arterial smooth muscle cells. Am J Physiol Cell Physiol 304: C324 –C333, 2012.
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Letter to the Editor
Letter to the editor: “Why isn’t clinical experience with ouabain more widely accepted?” Hauke Fürstenwerth Freelance Consultant, Leverkusen, Germany TO THE EDITOR:
In the article “Why isn’t endogenous ouabain more widely accepted?” (2), Mordecai P. Blaustein refers to Thomas Kuhn in stating that scientists tend to ignore ideas and data that don’t fit their preconceptions and often don’t even read (or digest) articles that fall outside their “comfort zone.” Such a behavior is certainly true for many scientists engaged in research on endogenous ouabain. How else can it be explained that in the many publications on endogenous ouabain, no reference is made to the clinical experience with ouabain in the treatment of heart disease? How else can one claim, ouabain causing heart damage despite well-documented positive clinical experience in the treatment of heart disease with ouabain? How else can one neglect current reports on cardio protection induced by ouabain (12)? How else can one assert that endogenous ouabain raises blood pressure although in clinical experience a reduction of high blood pressure in patients is observed on treatment with ouabain (8, 14, 15)? In addition, ouabain reduces blood pressure in several animal species (5). How else can one claim to be surprised by an antagonistic relationship between digoxin and ouabain when ouabain has been used effectively to treat digitalis intoxication? Corresponding reports are documented as early as 1902. Recent in vitro and in vivo studies confirm this well-known clinical observation (13). Ouabain has been widely used in Europe, and especially in Germany, to treat heart failure. As early as 1904, a standardized solution of the pure substance was commercialized by E. Merck, Darmstadt and Boehringer Mannheim as “g-Strophanthin Thoms.” This ouabain solution was used both intravenously (4) and orally administered in the treatment of heart diseases. In 1909, the French physician Henri Vaquez introduced the intravenous application of ouabain (“Ouabain-Arnaud”) in France (16, 17). Some medical centers in the United States, too, have used the “French preparations” to treat heart diseases (9). The database of the German Institute for Medical Documentation and Information records more than 20 orally administered ouabain preparations that were used in Germany after 1950. In 1949 Boehringer Mannheim introduced a version of ouabain formulated as a tablet for sublingual application under the brand name Strophoral. In clinical practice, inconsistent experiences were made with the use of Strophoral, which provoked doubts about the reliability of its absorption. Pharmacological studies led to the development of improved products such as Purostrophan Dragees, Alvoral mr, and Strodival mr that all were enteric coated preparations. Strophoperm, Strophinos, and Strophocor N were oleophilic solutions for sublingual administration. With these preparations the neces-
Address for reprint requests and other correspondence: H. Fürstenwerth, Unterölbach 3A, 51381 Leverkusen, Germany (e-mail: hauke@fuerstenwerth. com). H1262
sary dosage for reliable therapeutic results were achieved at a considerably lower dosages than with Strophoral. The daily dose of Strophoral often amounted to 20 –30 mg ouabain (7); for the Purostrophan enteric-coated tablets, 2– 6 mg/day were sufficient (18). The daily dose of Strophoperm with 0.5–1 mg ouabain compared in magnitude with intravenous-administered ouabain (1). After oral and perlingual administration of ouabain preparations, serum concentrations between 0.1 and 0.9 ng/ml have been measured (3, 6). Until well into the 1970s, total absorption of a drug was considered to be the relevant criterion and not serum concentration. Today drugs such as Aliskiren, whose absorption rate is about 3%, will not be rejected just because the absorption rate is too low. Aliskiren’s therapeutic effects derive from sufficiently high serum concentrations, not from the total amount absorbed. The same is true for drugs like Nisoldipine (5%), Dabigatranetextilat (6.5%), or Ramipril (15%), which have absorption rates comparable to that of ouabain. For ouabain, absorption rates of 10% have been measured (11). Thus, contrary to textbook knowledge handed down over the decades, ouabain in appropriate galenic formulations is suitable for oral administration. In addition to the uncertainty on the identity of endogenous ouabain (10), the ignorance of the extensive literature on the clinical experience with ouabain certainly contributes to the fact that endogenous ouabain “isn’t more widely accepted.” DISCLOSURES No conflicts of interest, financial or otherwise, are declared by the author. AUTHOR CONTRIBUTIONS H.F. drafted, edited, revised, and approved final version of manuscript. REFERENCES 1. Altmann K. Beitrag zur peroralen Strophanthintherapie. Med Klin (Munich) 47: 446 –448, 1952. 2. Blaustein MP. Why isn’t endogenous ouabain more widely accepted? Am J Physiol Heart Circ Physiol 307: H635–H639, 2014. 3. Erdle HP, Schultz KD, Wetzel E, Gross F. Resorption und Ausscheidung von g-Strophanthin nach intravenöser und perlingualer Gabe. Dtsch Med Wochenschr 104: 976 –979, 1979. 4. Fleischmann P, Wjasmensky H. Über intravenöse Strophanthintherapie bei Verwendung von gratus - Strophanthinum crystallisatum Thoms. Deutsche Medizinische Wochenschrift 35: 918 –921, 1909. 5. Fürstenwerth H. On correlation and causality. Crit Care Med 41: e140 – e141, 2013. 6. Greeff K, Köhler E, Strobach H, Verspohl E. Zur Pharmakokinetic des g-Strophanthin. Verh Dtsch Ges Kreislaufforsch 40: 301–305, 1974. 7. Halhuber M, Lantscherat T, Meusburger K. Zur Strophoraltherapie. Med Klin 36: 1440 –1443, 1954. 8. Kracke R. Zur perlingualen Strophanthintherapie. Dtsch Med Wochenschr 79: 81–83, 1954. 9. Levine SA. The potency of some French digitalis preparations. Boston Med Surg J 182: 64 –66, 1920. 10. Lewis LK, Yandle TG, Hilton PJ, Jensen BP, Begg EJ, Nicholls MG. Endogenous ouabain is not ouabain. Hypertension. 2014 Jul 7. pii: HYPERTENSIONAHA.114.03919. [Epub ahead of print].
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Letter to the Editor LETTER TO THE EDITOR 11. Marchetti GV, Marzo A, De Ponti C, Scalvini A, Merlo L, Noseda V. Blood levels and tissue distribution of 3 H-ouabain administered per os. An experimental and clinical study. Arzneimittelforschung 21: 1399 – 1403, 1971. 12. Morgan EE, Li Z, Stebal C, Belliard A, Tennyson G, Salari B, Garlid KD, Pierre SV. Preconditioning by subinotropic doses of ouabain in the Langendorff perfused rabbit heart. J Cardiovasc Pharmacol 55: 234 –239, 2010. 13. Nesher M, Shpolansky U, Viola N, Dvela M, Buzaglo N, Cohen Ben-Ami H, Rosen H, Lichtstein D. Ouabain attenuates cardiotoxicity induced by other cardiac steroids. Br J Pharmacol 160: 346 –354, 2010.
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14. Rothmund W. Über die Entstehung der essentiellen Hypertonie. Notabene Medici 7: 22–32, 1977. 15. United States Patent Office. United States Patent 4, 020, 159, Methods of, and medications for treating cardiac disorders by using strophanthin. Filed October 8, 1974 by Herbert K. G. 16. Vaquez H, Leconte. Les injections intraveneuses de strophanthine dans le traitement de l’insuffisance cardiaque. Bull. et mem. Soc. med d’hop, Paris, xvii, 662–679, 1909. 17. Vaquez H, Lutembacher L. Ouabaine. Arch Mal Coeur 10: 197, 1917. 18. Wiesend W. Über perorale Strophanthinbehandlung, besonders beim Altersherz. Münchener medizinische Wochenschrift 98: 900 –904, 1956.
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Am J Physiol Heart Circ Physiol 307: H1264–H1265, 2014; doi:10.1152/ajpheart.00571.2014.
Letter to the Editor
Reply to “Letter to the editor: ‘Why isn’t clinical experience with ouabain more widely accepted?’” Mordecai P. Blaustein Departments of Physiology and Medicine, University of Maryland School of Medicine, Baltimore, Maryland REPLY:
Fürstenwerth (12a) notes that my “Perspectives” on endogenous ouabain (EO) (2) 1) didn’t mention the use of ouabain as a therapeutic and antihypertensive agent (true; see last paragraph); 2) didn’t consider the view that “(EO) is not ‘ouabain’” (21) [I cited an earlier version (32) and the refutation (24); my article (2) was published online 4 days before Lewis and colleagues’ (21); see our responses to Lewis et al. (2a, 14)]; and 3) called the 1993 discovery of ouabaindigoxin antagonism (27) “a surprise,” despite the 2010 report that ouabain antagonizes acute digoxin and bufalin cardiotoxicity (31). Manunta et al. (26, 27) were, surely, the first to document that cardiotonic steroids (CTS) could antagonize one another and that all CTS do not have identical effects (e.g., ouabain, but not digoxin, causes hypertension). Thus this was “a surprise” in 1993. Nesher and colleagues (31) confirmed that ouabain and digoxin antagonize one another acutely but didn’t address the mechanism (41). The mechanism for antagonizing the chronic effects of ouabain (26, 27), not studied by Nesher, is apparently more complex (47). Fürstenwerth cites the Lewis/Hilton/Nichols group (21) regarding “uncertainty on the identity of EO.” The repeatedly verified analytical (HPLC plus mass spectroscopy, nuclear magnetic resonance, and UV) evidence that mammalian (including human) EO is, in fact, “ouabain” (13, 16 –18, 39, 42) is not mentioned, although this contradicts the Lewis et al. view (21). The latter had already been refuted twice (23, 24). Moreover, much additional, independent, but generally overlooked evidence confirms that the endogenous substance is chemically very “ouabain-like.” First, ouabain-resistant mutation of the ␣2 Na⫹ pump ouabain binding site abolishes the hypertensinogenic actions of ACTH and ouabain (10, 11, 22), proof that an EO-like ligand binds to this receptor. Second, prolonged subcutaneous administration of ouabain, but not digoxin, induces hypertension in rodents (15, 26, 44, 47). Ouabain’s effect has been replicated in numerous laboratories in the United States, Brazil, Canada, China, and Italy. Third, ouabain, but not digoxin, also increases expression of Ca2⫹ transporters, including Na⫹/Ca2⫹ exchanger-1 in arteries (47). Similar upregulation of these arterial transporters occurs in many forms of hypertension (4, 35, 36, 46). Fourth, digoxin blocks both the ouabain-induced protein upregulation (47) and hypertension (15, 26, 27). Fifth, complexation of EO with Fab fragments that bind digoxin and ouabain with high affinity (37, 38) abolishes several forms of hypertension (4), including those induced by ACTH (10), ouabain (10, 15), and high dietary salt (15). Sixth, reduced expression of ␣2 Na⫹ pumps (the EO receptors), equivalent to ␣2 Na⫹ pump inhibition by Address for reprint requests and other correspondence: M. P. Blaustein, Dept. of Physiology, Univ. of Maryland School of Medicine, 655 W. Baltimore St., Baltimore, MD 21201 (e-mail: [email protected]). H1264
nanomolar EO/ouabain, induces hypertension (5, 7, 45), whereas ␣2 overexpression lowers blood pressure (BP) (7, 34). Given these many related, consistent, and widely replicated observations, the burden is on the few groups (1, 9, 21) that have been unable to purify EO or to induce hypertension with ouabain to explain why not. Contradictory observations can’t both be correct, and negative results are not proof that EO is not ouabain. One must distinguish solid data from artifacts of experimental design and/or execution. It’s highly unlikely that EO spectra from five independent laboratories are all artifacts or that the ⬎12 laboratories that have described ouabaininduced hypertension in rodents are all wrong. Undoubtedly, EO has beneficial effects (30). Plasma EO is increased in normal pregnancy (16), and pregnant mice with ouabain-resistant ␣2 Na⫹ pumps have low BP (33). Plasma EO is also elevated during salt depletion (3, 25), and its acute and chronic vasotonic effects likely help minimize BP decline (3). Acutely, ouabain/EO can enhance cardiac and vascular (6, 20, 43) contractility. Nevertheless, acute intravenous administration of ouabain not only increases resistance to blood flow in humans (28) but, in hypertensive patients, may have devastating cerebrovascular and cardiovascular effects (19). Tests of oral ouabain clinical efficacy cited by Fürstenwerth are anecdotal. There are no controlled clinical trials and certainly none that compare efficacy to plasma ouabain level, a crucial problem, given the low and irregular absorption of oral ouabain (12). Indeed, ignorance of EO and lack of controlled trials continues to undermine all clinical studies of cardiotonic steroid efficacy [e.g., (8, 29, 40)]. Absent quality data, there is little rationale for discussing the clinical use of ouabain. DISCLOSURES No conflicts of interest, financial or otherwise, are declared by the author. AUTHOR CONTRIBUTIONS M.P.B. drafted, edited, revised, and approved final version of manuscript. REFERENCES 1. Baecher S, Kroiss M, Fassnacht M, Vogeser M. No endogenous ouabain is detectable in human plasma by ultra-sensitive UPLC-MS/MS. Clin Chim Acta 431: 87–92, 2014. 2. Blaustein MP. “Why isn’t endogenous ouabain more widely accepted?” Am J Physiol Heart Circ Physiol 307: H635–H639, 2014. 2a.Blaustein MP. Re:Re:Re: “Endogenous Ouabain is Not Ouabain” by Lewis et al. Hypertension (Online First on July 7, 2014; doi: 10.1161/ HYPERTENSIONAHA.114.03919). Epub Comment, August 25, 2014. 3. Blaustein MP, Chen L, Li M, Gao J, Hamlyn JM. Angiotensin II triggers the same pressor mechanisms in salt-sensitive hypertension and during salt depletion. Hypertension 62: A19, 2013. 4. Blaustein MP, Leenen FH, Chen L, Golovina VA, Hamlyn JM, Pallone TL, Van Huysse JW, Zhang J, Wier WG. How NaCl raises blood pressure: a new paradigm for the pathogenesis of salt-dependent hypertension. Am J Physiol Heart Circ Physiol 302: H1031–H1049, 2012. 5. Blaustein MP, Zhang J, Chen L, Song H, Raina H, Kinsey SP, Izuka M, Iwamoto T, Kotlikoff MI, Lingrel JB, Philipson KD, Wier WG, Hamlyn JM. The pump, the exchanger, and endogenous ouabain: signal-
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Letter to the Editor LETTER TO THE EDITOR ing mechanisms that link salt retention to hypertension. Hypertension 53: 291–298, 2009. 6. Bova S, Blaustein MP, Ludens JH, Harris DW, DuCharme DW, Hamlyn JM. Effects of an endogenous ouabainlike compound on heart and aorta. Hypertension 17: 944 –950, 1991. 7. Chen L, Song H, Kotlikoff MI, Lee J, Pritchard TJ, Paul RJ, Li M, Blaustein MP. Blood pressure correlates directly with the expression level of high ouabain affinity alpha-2 Na⫹ pumps in arterial smooth muscle. Hypertension 62: A19, 2013. 8. Digitalis Investigative Group. The effect of digoxin on mortality and morbidity in patients with heart failure. N Engl J Med 336: 525–533, 1997. 9. Doris PA, Jenkins LA, Stocco DM. Is ouabain an authentic endogenous mammalian substance derived from the adrenal? Hypertension 23: 632– 638, 1994. 10. Dostanic-Larson I, Van Huysse JW, Lorenz JN, Lingrel JB. The highly conserved cardiac glycoside binding site of Na,K-ATPase plays a role in blood pressure regulation. Proc Natl Acad Sci USA 102: 15845–15850, 2005. 11. Dostanic I, Paul RJ, Lorenz JN, Theriault S, Van Huysse JW, Lingrel JB. The ␣2-isoform of Na-K-ATPase mediates ouabain-induced hypertension in mice and increased vascular contractility in vitro. Am J Physiol Heart Circ Physiol 288: H477–H485, 2005. 12. Erdle HP, Schultz KD, Wetzel E, Gross F. Absorption and excretion of g-strophanthin after intravenous or sublingual administration [Author’s translation]. Dtsch Med Wochenschr 104: 976 –979, 1979. 12a.Fürstenwerth H. Letter to the editor: “Why isn’t clinical experience with ouabain more widely accepted?” Am J Physiol Heart Circ Physiol 307; doi:10.1152/ajpheart.00525.2014. 13. Hamlyn JM, Blaustein MP, Bova S, DuCharme DW, Harris DW, Mandel F, Mathews WR, Ludens JH. Identification and characterization of a ouabain-like compound from human plasma. Proc Natl Acad Sci USA 88: 6259 –6263, 1991. 14. Hamlyn JM, Manunta P, Blaustein MP. “Endogenous Ouabain is Not Ouabain” by Lewis et al. (Online First on July 7, 2014; doi:10.1161/ HYPERTENSIONAHA.114.03919). Hypertension Epub Comment, July 28, 2014. 15. Huang BS, Kudlac M, Kumarathasan R, Leenen FH. Digoxin prevents ouabain and high salt intake-induced hypertension in rats with sinoaortic denervation. Hypertension 34: 733–738, 1999. 16. Jacobs BE, Liu Y, Pulina MV, Golovina VA, Hamlyn JM. Normal pregnancy: mechanisms underlying the paradox of a ouabain-resistant state with elevated endogenous ouabain, suppressed arterial sodium calcium exchange, and low blood pressure. Am J Physiol Heart Circ Physiol 302: H1317–H1329, 2012. 17. Kawamura A, Guo J, Itagaki Y, Bell C, Wang Y, Haupert GT, Jr., Magil S, Gallagher RT, Berova N, Nakanishi K. On the structure of endogenous ouabain. Proc Natl Acad Sci USA 96: 6654 –6659, 1999. 18. Komiyama Y, Nishimura N, Dong XH, Hirose S, Kosaka C, Masaki H, Masuda M, Takahashi H. Liquid chromatography mass spectrometric analysis of ouabainlike factor in biological fluid. Hypertens Res 23, Suppl: S21–S27, 2000. 19. Kumar R, Yankopoulos NA, Abelmann WH. Ouabain-induced hypertension in a patient with decompensated hypertensive heart disease. Chest 63: 105–108, 1973. 20. Lee CO, Kang DH, Sokol JH, Lee KS. Relation between intracellular Na ion activity and tension of sheep cardiac Purkinje fibers exposed to dihydro-ouabain. Biophys J 29: 315–330, 1980. 21. Lewis LK, Yandle TG, Hilton PJ, Jensen BP, Begg EJ, Nicholls MG. Endogenous ouabain is not ouabain. Hypertension 2014 Jul 7. pii: doi: 10.1161/HYPERTENSIONAHA.114.03919. [Epub ahead of print]. 22. Lorenz JN, Loreaux EL, Dostanic-Larson I, Lasko V, Schnetzer JR, Paul RJ, Lingrel JB. ACTH-induced hypertension is dependent on the ouabain-binding site of the ␣2-Na⫹-K⫹-ATPase subunit. Am J Physiol Heart Circ Physiol 295: H273–H280, 2008. 23. Manunta P, Ferrandi M. Different effects of marinobufagenin and endogenous ouabain. J Hypertens 22: 257–259, 2004. 24. Manunta P, Ferrandi M, Bianchi G, Hamlyn JM. Endogenous ouabain in cardiovascular function and disease. J Hypertens 27: 9 –18, 2009. 25. Manunta P, Hamilton BP, Hamlyn JM. Salt intake and depletion increase circulating levels of endogenous ouabain in normal men. Am J Physiol Regul Integr Comp Physiol 290: R553–R559, 2006. 26. Manunta P, Hamilton J, Rogowski AC, Hamilton BP, Hamlyn JM. Chronic hypertension induced by ouabain but not digoxin in the rat:
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