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

We have previously reported that ATP-inhibitable K+ channels, in vesicles d erived from the basolateral membrane of Necturus maculosus small intestinal cells, exhibit volume regulatory responses that resemble those found in th e intact tissue after exposure to anisotonic solutions. We now report that increases in K+ channel activity can also be elicited by exposure of these vesicles to isotonic solutions containing glucose or alanine that equilibra te across these membranes. We also demonstrate that swelling after exposure to a hypotonic solution or an isotonic solution containing alanine or gluc ose reduces inhibition of channel activity by ATP and that this finding can not be simply attributed to dilution of intravesicular ATP. We conclude tha t ATP-sensitive, stretch-activated K+ channels may be responsible for the w ell-established increase in basolateral membrane K+ conductance of Necturus small intestinal cells after the addition of sugars or amino acids to the solution perfusing the mucosal surface, and we propose that increases in ce ll volume, resulting in membrane stretch, decreases the sensitivity of thes e channels to ATP.