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Printed in Great Britain TETRAETHYLAMMONIUM-SENSITIVE APICAL K+ CHANNELS MEDIATING K+ SECRETION BY TURTLE COLON

By J. Wilkinson, Nancy L. Kushman and David C. Dawson

Abstract

1. Apical membrane K+ channels in turtle colon were identified and characterized using current fluctuation analysis. 2. Under short-circuit conditions in NaCl-Ringer solution, the power density spectrum (PDS) of the short-circuit current (I.C) sometimes exhibited a clearly discernible Lorentzian component, indicating spontaneous fluctuations produced by a population of apical ion channels. The Lorentzian component had a characteristic corner frequency (fe) which averaged 10-2+0-9 Hz (mean+s.E.M., n = 20). 3. The power of the spontaneous fluctuations was enhanced (S. increased) by manoeuvres that depolarize the apical membrane electrical potential (Va). Discernible fluctuations were enhanced or induced by raising the serosal K+ concentration ([K+],- 50-115 mm, Na+ replacement), by clamping the transepithelial potential (Vt) to serosa-positive values, or by blocking basolateral K+ channels with Ba2+. 4. Mucosal amiloride (100,UM) attenuated the spontaneous fluctuations observed in NaCl-Ringer solution but had no effect in the presence of serosal high K+, indicating that amiloride did not block the K+-permeable channels but these channels resided in the same cells as the amiloride-sensitive Na+ channels

Year: 1991
OAI identifier: oai:CiteSeerX.psu:10.1.1.1003.3721
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