Potassium channels in basolateral membrane vesicles from necturus enterocytes: stretch and ATP sensitivity

We have previously reported that ATP-inhibitable K⁺channels, in vesicles derived from the basolateral membrane ofNecturus maculosus small intestinal cells, exhibit volumeregulatory responses that resemble those found in the intact tissueafter exposure to anisotonic solutions. We now report that increases inK⁺ channel activity can also be elicited by exposure ofthese vesicles to isotonic solutions containing glucose or alanine thatequilibrate across these membranes. We also demonstrate that swellingafter exposure to a hypotonic solution or an isotonic solutioncontaining alanine or glucose reduces inhibition of channel activity byATP and that this finding cannot be simply attributed to dilution ofintravesicular ATP. We conclude that ATP-sensitive, stretch-activated K⁺ channels may be responsible for the well-establishedincrease in basolateral membrane K⁺ conductance ofNecturus small intestinal cells after the addition of sugarsor amino acids to the solution perfusing the mucosal surface, and wepropose that increases in cell volume, resulting in membrane stretch,decreases the sensitivity of these channels to ATP.