title: Reconstitution of a KATP channel from basolateral membranes of Necturus enterocytes.
abstract: We have previously reported that basolateral membrane vesicles isolated from Necturus maculosa small intestinal epithelial cells and incorporated into planar phospholipid bilayers display a highly selective "maxi"-conductance K+ channel whose open-time probability is affected by voltage. We now report that this channel is inhibited by MgATP in the solution bathing the intracellular face of the channel but not by Mg2+ or the Na+ or K+ salts of ATP; the effects of MgATP can be prevented or reversed by MgADP. The channel is also inhibited by the nonhydrolyzable ATP analogue magnesium adenosine 5'-O-(3-thiotriphosphate) and the sulfonylurea derivatives tolbutamide and glibenclamide; all of these agents are effective in the intracellular compartment but not when added to the extracellular compartment alone. Channel activity is stimulated by the "K+ channel opener," diazoxide, which also reverses the effect of glibenclamide but not of MgATP. The possible role of this channel as a mediator of the parallelism between basolateral membrane Na(+)-K+ pump activity and the macroscopic K+ conductance of that barrier is discussed.
authors.affiliation: Department of Integrative Biology, University of Texas Medical School at Houston 77225, USA.
authors.forename: O
authors.initials: O
authors.lastname: Mayorga-Wark
authors.forename: W P
authors.initials: WP
authors.lastname: Dubinsky
authors.forename: S G
authors.initials: SG
authors.lastname: Schultz
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology / Q000502:physiology*; D000818:Animals; D003981:Diazoxide / Q000494:pharmacology; D005905:Glyburide / Q000494:pharmacology; D007421:Intestine, Small / Q000166:cytology / Q000378:metabolism*; D008566:Membranes / Q000378:metabolism; D009337:Necturus; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D014044:Tolbutamide / Q000494:pharmacology
chemical_list: D015221:Potassium Channels; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D014044:Tolbutamide; D003981:Diazoxide; D005905:Glyburide