Characteristics of two basolateral potassium channel populations in human colonic crypts.
The basolateral membrane of human colonic crypt cells contains Ca2+ and cAMP activated, Ba2+ blockable, low conductance (23 pS) K+ channels, which probably play an important part in intestinal Cl- secretion. This study has defined more clearly the basolateral K+ conductive properties of human colonic crypts using patch clamp recording techniques. High conductance (138 pS) K+ channels were seen in 25% of patches (one or two channels per patch), and significantly inhibited by the addition of 5 mM Ba2+, 1 mM quinidine or 20 mM tetraethylammonium chloride (TEA) to the cytosolic side of excised inside-out patches, whereas 1 mM diphenylamine-2-carboxylic acid (DPC) had no effect. In contrast, clusters of the 23 pS K+ channel (two to six channels per patch) were present in > 75% of patches, and channel activity was inhibited by quinidine and DPC, but not by TEA. Activity of the 138 pS K+ channel in inside-out patches was abolished almost completely by removal of bath Ca2+, but in contrast with its effect on the 23 pS K+ channel, addition of 0.1 mM carbachol had no effect on the 138 pS K+ channel in cell attached patches. It is concluded that human colonic crypt cells possess two discrete basolateral K+ channel populations, which can be distinguished by their responses to K+ channel blockers, and their different sensitivities to changes in intracellular Ca2+ concentration.
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Department of Medicine Gastrointestinal Molecular Physiology Group, (University of Manchester), Salford.
Warhurst
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Sandle
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D016022:Case-Control Studies; D003106:Colon / Q000737:chemistry*; D006801:Humans; D007413:Intestinal Mucosa / Q000737:chemistry*; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D011802:Quinidine / Q000494:pharmacology; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D062367:ortho-Aminobenzoates / Q000494:pharmacology
D026902:Potassium Channel Blockers; D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; D062367:ortho-Aminobenzoates; D019789:Tetraethylammonium; C001209:fenamic acid; D011802:Quinidine