84:1424-31 3 Knowles MR, Church NL, Waltner WE, Yankaskas JR, Gilligan PH, King M, et a1. A pilot study of aerosolized amiloride for the treatment of cystic fibrosis lung disease. N Eng) J Med 1990; 322:1189-94 4 Mason SJ, Paradiso AM, Boucher RC. Regulation of transepithelial ion transport and intracellular calcium by extracellular adenosine triphosphate in human normal and cystic fibrosis airway epithelium. Br J PharmacoI1991; 103:1649-56 5 Knowles MR, Clarke LL, Boucher RC. Activation by extracellular nucleotides of chloride secretion in the airway epithelia of patients with cystic fibrosis. N Eng) J Med 1991; 325:533-77 6 Knowles M, Gatzy J, Boucher R. Increased bioelectric potential difference across respiratory epithelia in cystic fibrosis. N Engl J Med 1981; 305:1489-95 7 Knowles M, Gatzy J, Boucher R. Relative ion permeability of normal and cystic fibrosis nasal epithelium. J Clin Invest 1983; 71:1410-17 8 Willumsen NJ, Davis C~ Boucher RC. Intracellular ct activity and cellular pathways in cultured human airway epithelium. Am J Physiol 1989; 256:1033-44 9 Willumsen NJ, Boucher RC. Shunt resistance and ion permeabilities in normal and cystic fibrosis airway epithelium. Am J Physioll989; 256:1054-63 10 Willumsen NJ, Davis C~ Boucher RC. Cellular ct transport in cultured cystic fibrosis airway epithelium. Am J PhysioI1989; 256: 1045-53 11 Burnstock G. Overview: purinergic mechanisms. Ann NY Acad Sci 1990; 603:1-18 12 O'Connor SE, Dainty lA, Leff E Further subclassification of ATP receptors based on agonist studies. Trends Pharmacol Sci 1991; 12:137-41 13 Dubyak G, Cohen DS. Activation of inositol phospholipid specific phosphylipase C by P2 purinergic receptors on human phagocytic leukocytes: role of pertussis toxin sensitive G proteins. Ann NY Acad Sci 1990; 603:227-45 14 Paradiso AM, Cheng EHC, Boucher RC. Effects of bradykinin on intracellular calcium regulation in human ciliated airway epithelium. Am J Physioll991; 261:63-69 15 Cushley MJ, Tattersfield AE, Holgate ST. Inhaled adenosine guanosine on airway resistance in normal and asthmatic subjects. Br J Clio Pharmacol 1983; 15:161-65 16 Biological actions of extracellular ATE New York: The New York Academy of Sciences, 1990

Effects of Endothelin-1 on Tracheal Submucosal Gland Secretion and Epithelial Function in the Ferret* S.E. Webber, Ph.D.; E. Yurdako~ M.D.; A.]. Woods, Ph.D.; and ].G. Widdicombe, M.D.

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ndothelin-l (ET-l) is one of a family of novel peptides recently discovered in the human genome} It was originally isolated from cultured porcine aortic endothelial cells2 and is a potent constrictor of isolated blood vessels. 3 ET-l is also the most potent ofthe endothelins at contracting bronchial smooth muscle." Immunofluorescent staining for ET-l has been found in epithelial cells from the hilum to the periphery of the

*From the Department of Physiology, St George's Hospital Medical School, London, England.

conducting airways of mice, s and epithelial cells from human bronchi form and release endothelin-like material. 6 However, the effects of ET-l on airway mucosal tissues, including submucosal glands and the epithelium itself, have not been studied. The ferret trachea in vitro is a preparation which allows the simultaneous measurement of a number of airway functions, and we have used this preparation to assess the activity ofET-l on baseline smooth muscle tone, submucosal gland secretion (lysozyme secretion from serous cells), and epithelial function and integrity (active epithelial albumin transport and transepithelial potential difference [PD D. We have also examined the effect of ET-l on responses to the muscarinic agonist methacholine and the a-adrenoreceptor agonist, phenylephrine. The contraction ofbronchial smooth muscle by ET-l may be mediated through activation of dihydropyridine-sensitive Ca2 + channels." l'he role of these Ca2 + channels in the responses to ET-l in the present study was assessed using the Ca2 + channel blocker, nifedipine. METHODS

The trachea was removed from the ferret, cannulated at both ends, and mounted laryngeal end downwards in an organ bath. The trachea was bathed on the submucosal side with Krebs buffer

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-0.8 FIGURE 1. Concentration-response curves for the effect of ET-1 on (a, upper) intraluminal tracheal pressure and (b, lower) transepitheIiaI PD in the ferret trachea in vitro. Points are means of 6 determinations and the vertical bars are SEM. Asterisks indicate signi6cant (p