Electrical characteristics of inward-rectifying K+ channels in isolated bullfrog oxyntic cells.
The properties of K+ channels in the isolated oxyntic cells of the bullfrog (Rana catesbeiana) were investigated using the patch-clamp method. Two types of K+ channels on the basolateral membrane were identified on the basis of their electrophysiological and pharmacological properties. The K+ channel most frequently observed has a single-channel conductance of 61.0 +/- 2.9 pS (n = 10) and is activated by an increase in intracellular Ca2+. The other K+ channel has a single-channel conductance of 30.3 +/- 2.7 pS (n = 7), which is activated by adenosine 3',5'-cyclic monophosphate (cAMP). The physiological and pharmacological characteristics common to the two K+ channels are inward-going rectification with a high selectivity for K+ and indirect inhibition by omeprazole. The inward rectification is controlled by intracellular Mg2+ in such a way that the more Mg2+ is applied intracellularly, the more their inward-rectifying property is enhanced. The finding that bethanechol and cAMP increase the open probability of these K+ channels as well as activating the acid secretion indicates that there may be a relationship between these two processes in the oxyntic cells.
First Department of Internal Medicine, Hiroshima University School of Medicine, Japan.
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Mieno
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Kajiyama
D000818:Animals; D018723:Bethanechol; D001626:Bethanechol Compounds / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002469:Cell Separation; D000242:Cyclic AMP / Q000494:pharmacology; D004594:Electrophysiology; D008274:Magnesium / Q000494:pharmacology; D009853:Omeprazole / Q000494:pharmacology; D010295:Parietal Cells, Gastric / Q000378:metabolism*; D015221:Potassium Channels / Q000502:physiology*; D011892:Rana catesbeiana
D001626:Bethanechol Compounds; D015221:Potassium Channels; D018723:Bethanechol; D000242:Cyclic AMP; D008274:Magnesium; D009853:Omeprazole; D002118:Calcium