title: Dietary potassium modulates active potassium absorption and secretion in rat distal colon.
abstract: To determine the effect of variations in body stores of potassium on the rate of active potassium transport in the large intestine, unidirectional 42K fluxes were performed under short-circuit conditions across isolated distal colonic mucosa of control, dietary potassium-depleted and dietary potassium-loaded rats. Potassium depletion stimulated net potassium absorption (JK net) (0.87 +/- 0.19 vs. 0.49 +/- 0.04 mu eq X h-1 X cm-2, P less than 0.025) due to a 40% increase in mucosal-to-serosal potassium transport (JK m----s). In sodium-free Ringer solution JK net in the potassium-depleted group was also significantly greater than in controls (1.93 +/- 0.26 vs. 1.01 +/- 0.11 mu eq X h-1 X cm-2, P less than 0.005). In contrast, in chloride-free Ringer solution JK net was identical in the control and potassium-depleted groups (0.39 +/- 0.05 vs. 0.46 +/- 0.07 mu eq X h-1 X cm-2, P = NS). Potassium loading reversed net potassium absorption to net potassium secretion (-0.76 +/- 0.08 mu eq X h-1 X cm-2, P less than 0.001) as the result of a decrease in JK m----s and an increase in serosal-to-mucosal potassium transport (JK s----m). Net potassium secretion was abolished in the absence of either sodium or chloride from the bathing solution but not by mucosal amiloride. In sodium-free Ringer solution JK net was similar in control and potassium-loaded groups, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D003106:Colon / Q000502:physiology*; D004032:Diet; D007408:Intestinal Absorption / Q000187:drug effects*; D007700:Kinetics; D008297:Male; D011188:Potassium / Q000008:administration & dosage / Q000494:pharmacology / Q000502:physiology*; D011522:Protons; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism
chemical_list: D011522:Protons; D000584:Amiloride; D012964:Sodium; D011188:Potassium