title: Control of potassium transport by turtle colon: role of membrane potential.
abstract: To more clearly define the role of the transepithelial electrical potential difference (V m----s), potassium permeability, and sodium-potassium pump rate in transcellular potassium transport by isolated turtle colon, we measured transmural potassium fluxes under open-circuit conditions in the presence and absence of putative blockers of potassium transport: amiloride and barium. The results were consistent with the notion that V m----s is a major determinant of cellular potassium secretion, whereas active potassium absorption is insensitive to changes in V m----s. These observations suggest that "coupling" between colonic sodium absorption and potassium secretion in vivo could be due primarily to the effect of the lumen negative V m----s on transcellular secretory potassium flow. Amiloride-induced inhibition of potassium secretion appeared to be due to the reductions in V m----s and sodium-potassium pump rate that accompanied the inhibition of active sodium absorption.
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000494:pharmacology; D001693:Biological Transport, Active; D002463:Cell Membrane Permeability; D003106:Colon / Q000187:drug effects / Q000378:metabolism*; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology; D008564:Membrane Potentials; D011188:Potassium / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D014426:Turtles / Q000378:metabolism*
chemical_list: D007473:Ion Channels; D001464:Barium; D000584:Amiloride; D012964:Sodium; D011188:Potassium