Effect of saralasin upon plasma in hypertensive patients
catecholamines
Nicolas D. Vlachakis, M.D. Artur B. Rib&o, M.D. Lawrence R. Krakoff, M.D. New York, N. Y.
Saralasin, (sarcosine 1, alanine 8, angiotensin II) a peptide antagonist of the vascular action of angiotensin II, reduces arterial pressure in subjects with high levels of circulating renin.‘, 2 However, during the first few minutes of administration of saralasin, a pressor response is often observed regardless of the effect of more prolonged action of the drug.3* 4 The transient pressor action of saralasin might be explained by the hormones of the adrenal medulla, for it has been demonstrated that angiotensin and other peptides release epinephrine and norepinephrine from this organ.5 Also, it has recently been reported that a hypertensive crisis occurred during infusion of saralasin in a patient with pheochromocytoma.6 In order to assess the significance of catecholamines from the adrenal medulla in the transient pressor action of saralasin, the effect of this peptide upon hemodynamics and plasma catecholamine concentration was compared to the effect of catecholamine infusion. Methods
Saralasin infusion studies were carried out in six patients. Noradrenaline infusions were performed in seven patients. Pheochromocytoma was excluded by determination of urine metaFrom the Hypertension Division, Department of Medicine, Mount Sinai School of Medicine of the City University of New York. Supported by United States Public Health Service Grant HL 13595 and by Clinical Center Grant RR-71. Received for publication May 3, 1977. Accepted for publication June 16, 1977. Reprint requests: Lawrence R. Krakoff, M.D., Associate Professor of Medicine, Chief, Hypertension Division, Mount Sinai School of Medicine, Fifth Avenue and 100th St., New York, N. Y. 10029.
78
nephrine excretion in all subjects prior to any infusion studies. Infusion studies were performed during hospitalization while patients were ingesting diets containing 80 to 100 mEq. sodium. Diuretics were not administered. Infusion studies were carried out in the supine position. At one minute intervals blood pressure was measured by the Roche Arteriosonde 1216 and cardiac rate was monitored by electrocardiogram. Saralasin was given intravenously at a dose of 10 pg/Kg./ minute for a 30 minute period. Blood samples for plasma noradrenaline and adrenaline were taken from an indwelling catheter prior to infusion, after five minutes (just after the peak of the pressor response) and at the end of the infusion. Noradrenaline was given at a rate of 0.1 hg/Kg,/ minute for 15 minutes and blood samples were obtained just before and at the end of the infusion. Blood pressure measurements represent the difference between the means of 10 control determinations prior to infusion and of three determinations bracketing the time reported (i.e., for five minutes the mean of blood pressure taken at 4,5, and 6 minutes). Plasma catecholamine concentrations were determined by a sensitive and specific radioassay. Forty to 100 fl aliquots of plasma in which catecholamines are preserved by the use of EGTA and glutathione are incubated with 3H-methyl Sadenosyl methionine and catechol O-methyl transferase to form metanephrine and normetanephrine. These amines are separated by thin layer chromatography and converted to vanillin by periodate oxidation. Interassay variation is less than 10 per cent and the absolute sensitivity is 1.0 picogram for either adrenaline or noradrenaline.
January
1978, Vol. 95, NO. 1, pp. 78-80
Saralasin Results
catecholamines
I. Effect of saralasin upon mean arterial pressure (MAP) heart rate (HR), plasma noradrenaline (NA) and adrenaline (A) concentration after 5 and 30 minutes of infusion
Table
The effect of saralasin infusion upon mean arterial pressure, heart rate, and plasma catecholamine concentrations is shown in Table I. After five minutes of infusion mean arterial pressure rose significantly. Heart rate fell slightly, but the change was not statistically significant. At the end of the 30 minute saralasin infusion the mean arterial pressure was not significantly different from control for the entire group. Mean arterial pressure rose 5 to 13 mm. Hg in four patients, remained unchanged in one, and fell 9 mm. Hg in one (a patient with renal artery stenosis). Neither plasma noradrenaline nor plasma adrenaline was significantly different from pre-infusion levels at the end of the saralasin infusion. Table II demonstrates the effect of noradrenaline infusion. Mean arterial pressure rose significantly and to a degree comparable to the change observed during the first five minutes of saralasin infusion. Heart rate fell significantly. However, the change in heart rate produced by noradrenaline infusion was not significantly different from that observed during the first 5 minutes of saralasin infusion. The large increase in plasma noradrenaline concentration observed during noradrenaline infusion was 13 times that observed during the first five minutes of saralasin administration. A small but significant increase in plasma adrenaline concentration was observed during noradrenaline infusion. Discussion
Several of the angiotensins and structurally related peptides, including those with antagonist action produced by substitution of alanine for phenylalanine in the 8 or C terminal position, have been shown to release catecholamines from the adrenal medulla.” If this release were to have any physiologic action in man it might be expected that an increase in arterial pressure would be accompanied by an increase in heart rate, since adrenaline is the predominant catecholamine of human adrenal medulla.” The effect of saralasin infusion during the first five minutes of administration was to cause an increase in arterial pressure without any signticant change in cardiac rate. The alterations in plasma catecholamine concentration at this point were limited to a small but significant increase in plasma noradrenaline concentration without an appreciable change in adrenaline. More prolonged
American
and plasma
Heart
Jownal
MAP (mm. Hg) HR (beatdmin.) Plasma NA h3.h-U Plasma A (pg./ml.)
/ Control
/ Minks
/
I
I
I
127 + 5 73k 6 245 + 34 48+
+13 * 4* -4* 2 +115 + 28*’
5
+5*
All resultsareexpreesed ~8mean+ SEM. are the change from control
Valuea
iUin%s +4* 3 -2k 1 +30 f 23
2
+6+
at 6 and
4
30 minutes
level.
‘P c 0.025. **p < 0.01.
Table
MAP,
II. Effect of noradrenaline infusion upon HR, plasma NA and A concentrations Control
MAP (mm Hg.) HR (beatdmin.) Plasma NA (pg./ml.) Plasma A (pg./ml.) Results are expressed **p < 0.01.
117 k 3 76+ 3 332 rt 37 39* 5
Infusion +15 k 3** -7 -t 1** +1557 f x0** +13 + 3**
in Table I.
infusion of saralasin was no longer associated with any significant change in concentration of either plasma catecholamine. Since the hemodynamic changes observed during the first few minutes of saralasin infusion resembled that which might be due to alphaadrenergic stimulation, noradrenaline was infused at a rate which gave an increase in mean arterial pressure similar to that which was produced by saralasin at five minutes. Despite the similarity in change of arterial pressure, plasma noradrenaline rose to a much greater extent than was observed during saralasin infusion. Thus, although the hemodynamic changes associated with the transient pressor response to saralasin bear some similarity to what might be expected from an alpha-receptor antagonist, the amount of circulating noradrenaline measured during saralasin infusion fails to account for the observed change in pressure when compared to infusion of noradrenaline. The small increase in plasma noradrenaline detected during the initial pressure response to saralasin, while having no hemody-
79
Vlachakie,
Ribeiro,
and
Kraknff
namic significance per se, may indicate a trivial release from the adrenal medulla or an alteration in function of sympathetic neurons. Neuronal reuptake of noradrenaline plays an important role in terminating the action of the sympathetic neuro-transmitter,9 suggesting that changes in plasma catecholamines will reflect sympathetic neuronal activity to a very limited extent. The transient pressor effect of saralasin must be distinguished from the more prolonged elevation of arterial pressure that is observed when this drug is given to some hypertensive patients with low levels of circulating renin. The latter action of the peptide appears best related to a partial agonist function at the site of angiotensin II vascular receptors.l” While the observations presented in this study tend to exclude release of adreno-medullary catecholamines as a cause of the transient pressor action of saralasin, they do not eliminate the possibility that changes in neuro-secretion by adrenergic neurons may account for this phenomenon.
aline produced a hemodynamic pattern similar to that observed during the first five minutes of saralasin infusion. However, there was a thirteenfold increase of plasma noradrenaline observed when compared to the first five minutes of saralasin infusion. It was concluded that the transient pressor action of saralasin could not be explained by release of catecholamines from the adrenal medulla. However, the very slight increase in plasma norepinephrine observed during the first five minutes of saralasin infusion may imply altered function of sympathetic neurons. We express our thanks to the Company, Norwich, N. Y., for providing used in this study.
Pharmacal of saralasin
REFERENCES 1.
2.
Summary
3.
The effect of saralasin, a clinically employed angiotensin antagonist, upon hemodynamics and plasma catecholamine concentration was compared to the infusion of noradrenaline. These studies were carried out to determine if a transient pressor effect frequently observed during saralasin infusion might be mediated by release of catecholamines from the adrenal medulla. After five minutes of saralasin infusion, mean arterial pressure rose significantly, pulse rate fell slightly, and plasma noradrenaline increased by 115 t 28 pg./ml. Plasma adrenaline was unchanged. After 30 minutes of saralasin infusion, mean arterial pressure was at control levels and plasma catecholamine concentrations were also no different from pre-infusion levels. Infusion of noradren-
4.
80
Norwich supplies
5.
6.
7.
8. 9. 10.
Brunner, H. R., Gavras, H., Laragh, J. H., and Keenan, K.: Hypertension in man: Exposure of the renin and sodium components using angiotensin II blockade, Circ. Res. 34 (Suppl. 1):35, 1974. Streeten, D. H. P., Anderson, G. H., Freiberg, J. M., and Dalakos, T. G.: Use of an angiotensin II antagonist (saralasin) in the recognition of “angiotensinogenic” hypertension, N. Engl. J. Med. 292:657, 1975. Marks, L., Maxwell,, M. H., and Kaufman, J. J.: Saralasin bolus test, Lancet 11:784, 1975. Ribeiro, A. B., and Krakoff, L. R.: Angiotensin blockade in coarctation of the aorta, N. Engl. J. Med. 295:148, 1976. Peach, M. J.: Adrenal medullary stimulation induced by anaiotensin I. anaiotensin II. and analoaues. Circ. Res. 28and 29 (Suppi 11):107, 1971. Dunn, F. G., DeCarvalhb,, J. G. R., Kern, D. C., Higgins, J. R., and Frolich, E. D.: Pheochromocytoma crisis induced by saralasin, N. Engl. J. Med. 296:605, 1976. Passon, P. G. and Peuler, J. D.: A simplified radiometric assay for plasma norepinephrine and epinephrine, Anal. Biochem. 51:618, 1973. Williams, R. H., Ed.: Textbook of endocrinology, Philadelphia, Pa., 1974, W. B. Saunders Company, p. 309. Axelrod, J., and Weinshilboum, R.: Catecholamines, N. Engl. J. Med. 287:237, 1972. Hollenberg, N. K., Williams, G. H., Burger, B., Ishikawa, I., and Adams, D. F.: Blockade and stimulation of renal, adrenal, and vascular angiotensin II receptors with 1-sar, g-ala angiotensin II in normal man, J. Clin. Invest. 57:39, 1976.
January,
1978,
Vol.
95, No.
1
catecholamines
Nicolas D. Vlachakis, M.D. Artur B. Rib&o, M.D. Lawrence R. Krakoff, M.D. New York, N. Y.
Saralasin, (sarcosine 1, alanine 8, angiotensin II) a peptide antagonist of the vascular action of angiotensin II, reduces arterial pressure in subjects with high levels of circulating renin.‘, 2 However, during the first few minutes of administration of saralasin, a pressor response is often observed regardless of the effect of more prolonged action of the drug.3* 4 The transient pressor action of saralasin might be explained by the hormones of the adrenal medulla, for it has been demonstrated that angiotensin and other peptides release epinephrine and norepinephrine from this organ.5 Also, it has recently been reported that a hypertensive crisis occurred during infusion of saralasin in a patient with pheochromocytoma.6 In order to assess the significance of catecholamines from the adrenal medulla in the transient pressor action of saralasin, the effect of this peptide upon hemodynamics and plasma catecholamine concentration was compared to the effect of catecholamine infusion. Methods
Saralasin infusion studies were carried out in six patients. Noradrenaline infusions were performed in seven patients. Pheochromocytoma was excluded by determination of urine metaFrom the Hypertension Division, Department of Medicine, Mount Sinai School of Medicine of the City University of New York. Supported by United States Public Health Service Grant HL 13595 and by Clinical Center Grant RR-71. Received for publication May 3, 1977. Accepted for publication June 16, 1977. Reprint requests: Lawrence R. Krakoff, M.D., Associate Professor of Medicine, Chief, Hypertension Division, Mount Sinai School of Medicine, Fifth Avenue and 100th St., New York, N. Y. 10029.
78
nephrine excretion in all subjects prior to any infusion studies. Infusion studies were performed during hospitalization while patients were ingesting diets containing 80 to 100 mEq. sodium. Diuretics were not administered. Infusion studies were carried out in the supine position. At one minute intervals blood pressure was measured by the Roche Arteriosonde 1216 and cardiac rate was monitored by electrocardiogram. Saralasin was given intravenously at a dose of 10 pg/Kg./ minute for a 30 minute period. Blood samples for plasma noradrenaline and adrenaline were taken from an indwelling catheter prior to infusion, after five minutes (just after the peak of the pressor response) and at the end of the infusion. Noradrenaline was given at a rate of 0.1 hg/Kg,/ minute for 15 minutes and blood samples were obtained just before and at the end of the infusion. Blood pressure measurements represent the difference between the means of 10 control determinations prior to infusion and of three determinations bracketing the time reported (i.e., for five minutes the mean of blood pressure taken at 4,5, and 6 minutes). Plasma catecholamine concentrations were determined by a sensitive and specific radioassay. Forty to 100 fl aliquots of plasma in which catecholamines are preserved by the use of EGTA and glutathione are incubated with 3H-methyl Sadenosyl methionine and catechol O-methyl transferase to form metanephrine and normetanephrine. These amines are separated by thin layer chromatography and converted to vanillin by periodate oxidation. Interassay variation is less than 10 per cent and the absolute sensitivity is 1.0 picogram for either adrenaline or noradrenaline.
January
1978, Vol. 95, NO. 1, pp. 78-80
Saralasin Results
catecholamines
I. Effect of saralasin upon mean arterial pressure (MAP) heart rate (HR), plasma noradrenaline (NA) and adrenaline (A) concentration after 5 and 30 minutes of infusion
Table
The effect of saralasin infusion upon mean arterial pressure, heart rate, and plasma catecholamine concentrations is shown in Table I. After five minutes of infusion mean arterial pressure rose significantly. Heart rate fell slightly, but the change was not statistically significant. At the end of the 30 minute saralasin infusion the mean arterial pressure was not significantly different from control for the entire group. Mean arterial pressure rose 5 to 13 mm. Hg in four patients, remained unchanged in one, and fell 9 mm. Hg in one (a patient with renal artery stenosis). Neither plasma noradrenaline nor plasma adrenaline was significantly different from pre-infusion levels at the end of the saralasin infusion. Table II demonstrates the effect of noradrenaline infusion. Mean arterial pressure rose significantly and to a degree comparable to the change observed during the first five minutes of saralasin infusion. Heart rate fell significantly. However, the change in heart rate produced by noradrenaline infusion was not significantly different from that observed during the first 5 minutes of saralasin infusion. The large increase in plasma noradrenaline concentration observed during noradrenaline infusion was 13 times that observed during the first five minutes of saralasin administration. A small but significant increase in plasma adrenaline concentration was observed during noradrenaline infusion. Discussion
Several of the angiotensins and structurally related peptides, including those with antagonist action produced by substitution of alanine for phenylalanine in the 8 or C terminal position, have been shown to release catecholamines from the adrenal medulla.” If this release were to have any physiologic action in man it might be expected that an increase in arterial pressure would be accompanied by an increase in heart rate, since adrenaline is the predominant catecholamine of human adrenal medulla.” The effect of saralasin infusion during the first five minutes of administration was to cause an increase in arterial pressure without any signticant change in cardiac rate. The alterations in plasma catecholamine concentration at this point were limited to a small but significant increase in plasma noradrenaline concentration without an appreciable change in adrenaline. More prolonged
American
and plasma
Heart
Jownal
MAP (mm. Hg) HR (beatdmin.) Plasma NA h3.h-U Plasma A (pg./ml.)
/ Control
/ Minks
/
I
I
I
127 + 5 73k 6 245 + 34 48+
+13 * 4* -4* 2 +115 + 28*’
5
+5*
All resultsareexpreesed ~8mean+ SEM. are the change from control
Valuea
iUin%s +4* 3 -2k 1 +30 f 23
2
+6+
at 6 and
4
30 minutes
level.
‘P c 0.025. **p < 0.01.
Table
MAP,
II. Effect of noradrenaline infusion upon HR, plasma NA and A concentrations Control
MAP (mm Hg.) HR (beatdmin.) Plasma NA (pg./ml.) Plasma A (pg./ml.) Results are expressed **p < 0.01.
117 k 3 76+ 3 332 rt 37 39* 5
Infusion +15 k 3** -7 -t 1** +1557 f x0** +13 + 3**
in Table I.
infusion of saralasin was no longer associated with any significant change in concentration of either plasma catecholamine. Since the hemodynamic changes observed during the first few minutes of saralasin infusion resembled that which might be due to alphaadrenergic stimulation, noradrenaline was infused at a rate which gave an increase in mean arterial pressure similar to that which was produced by saralasin at five minutes. Despite the similarity in change of arterial pressure, plasma noradrenaline rose to a much greater extent than was observed during saralasin infusion. Thus, although the hemodynamic changes associated with the transient pressor response to saralasin bear some similarity to what might be expected from an alpha-receptor antagonist, the amount of circulating noradrenaline measured during saralasin infusion fails to account for the observed change in pressure when compared to infusion of noradrenaline. The small increase in plasma noradrenaline detected during the initial pressure response to saralasin, while having no hemody-
79
Vlachakie,
Ribeiro,
and
Kraknff
namic significance per se, may indicate a trivial release from the adrenal medulla or an alteration in function of sympathetic neurons. Neuronal reuptake of noradrenaline plays an important role in terminating the action of the sympathetic neuro-transmitter,9 suggesting that changes in plasma catecholamines will reflect sympathetic neuronal activity to a very limited extent. The transient pressor effect of saralasin must be distinguished from the more prolonged elevation of arterial pressure that is observed when this drug is given to some hypertensive patients with low levels of circulating renin. The latter action of the peptide appears best related to a partial agonist function at the site of angiotensin II vascular receptors.l” While the observations presented in this study tend to exclude release of adreno-medullary catecholamines as a cause of the transient pressor action of saralasin, they do not eliminate the possibility that changes in neuro-secretion by adrenergic neurons may account for this phenomenon.
aline produced a hemodynamic pattern similar to that observed during the first five minutes of saralasin infusion. However, there was a thirteenfold increase of plasma noradrenaline observed when compared to the first five minutes of saralasin infusion. It was concluded that the transient pressor action of saralasin could not be explained by release of catecholamines from the adrenal medulla. However, the very slight increase in plasma norepinephrine observed during the first five minutes of saralasin infusion may imply altered function of sympathetic neurons. We express our thanks to the Company, Norwich, N. Y., for providing used in this study.
Pharmacal of saralasin
REFERENCES 1.
2.
Summary
3.
The effect of saralasin, a clinically employed angiotensin antagonist, upon hemodynamics and plasma catecholamine concentration was compared to the infusion of noradrenaline. These studies were carried out to determine if a transient pressor effect frequently observed during saralasin infusion might be mediated by release of catecholamines from the adrenal medulla. After five minutes of saralasin infusion, mean arterial pressure rose significantly, pulse rate fell slightly, and plasma noradrenaline increased by 115 t 28 pg./ml. Plasma adrenaline was unchanged. After 30 minutes of saralasin infusion, mean arterial pressure was at control levels and plasma catecholamine concentrations were also no different from pre-infusion levels. Infusion of noradren-
4.
80
Norwich supplies
5.
6.
7.
8. 9. 10.
Brunner, H. R., Gavras, H., Laragh, J. H., and Keenan, K.: Hypertension in man: Exposure of the renin and sodium components using angiotensin II blockade, Circ. Res. 34 (Suppl. 1):35, 1974. Streeten, D. H. P., Anderson, G. H., Freiberg, J. M., and Dalakos, T. G.: Use of an angiotensin II antagonist (saralasin) in the recognition of “angiotensinogenic” hypertension, N. Engl. J. Med. 292:657, 1975. Marks, L., Maxwell,, M. H., and Kaufman, J. J.: Saralasin bolus test, Lancet 11:784, 1975. Ribeiro, A. B., and Krakoff, L. R.: Angiotensin blockade in coarctation of the aorta, N. Engl. J. Med. 295:148, 1976. Peach, M. J.: Adrenal medullary stimulation induced by anaiotensin I. anaiotensin II. and analoaues. Circ. Res. 28and 29 (Suppi 11):107, 1971. Dunn, F. G., DeCarvalhb,, J. G. R., Kern, D. C., Higgins, J. R., and Frolich, E. D.: Pheochromocytoma crisis induced by saralasin, N. Engl. J. Med. 296:605, 1976. Passon, P. G. and Peuler, J. D.: A simplified radiometric assay for plasma norepinephrine and epinephrine, Anal. Biochem. 51:618, 1973. Williams, R. H., Ed.: Textbook of endocrinology, Philadelphia, Pa., 1974, W. B. Saunders Company, p. 309. Axelrod, J., and Weinshilboum, R.: Catecholamines, N. Engl. J. Med. 287:237, 1972. Hollenberg, N. K., Williams, G. H., Burger, B., Ishikawa, I., and Adams, D. F.: Blockade and stimulation of renal, adrenal, and vascular angiotensin II receptors with 1-sar, g-ala angiotensin II in normal man, J. Clin. Invest. 57:39, 1976.
January,
1978,
Vol.
95, No.
1
