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Dietary potassium modulates active potassium absorption and secretion in rat distal colon



Dietary potassium modulates active potassium absorption and secretion in rat distal colon



American Journal of Physiology 251(5 Pt 1): G619-G626



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 .**GRAPHIC**. (0.87 .+-. 0.19 vs. 0.49 .+-. 0.04 .mu.eq .cntdot. h-1 .cntdot. cm-2, P < 0.025) due to a 40% increase in mucosal-to-serosal potassium transport .**GRAPHIC**. In sodium-free Ringer solution .**GRAPHIC**. in the potassium-depleted group was also significantly greater than in controls (1.93 .+-. 0.26 vs. 1.01 .+-. 0.11 .mu.eq .cntdot. h-1 .cntdot. cm-2, P < 0.005). In contrast, in chloride-free Ringer solution .**GRAPHIC**. was identical in the control and potassium-depleted groups (0.39 .+-. 0.05 vs. 0.46 .+-. 0.07 .mu.eq .cntdot. h-1 .cntdot. cm-2, P = NS). Potassium loading reversed net potassium absorption to net potassium secretion (-0.76 .+-. 0.08 .mu.eq .cntdot. h-1 .cntdot. cm-2, P < 0.001) as the result of a decrease in .**GRAPHIC**. and an increase in serosal-to-mucosal potassium transport .**GRAPHIC**. 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 .**GRAPHIC**. was similar in control and potassium-loaded groups, respectively. These data demonstrate that 1) potassium depletion stimulates an active potassium absorptive process that is sodium independent but chloride dependent, and 2) potassium loading stimulates a sodium-dependent, chloride-dependent potassium secretory process. Thus body stores of potassium modulate active potassium transport in the distal large intestine that may contribute to overall potassium homeostasis.

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Accession: 001564157

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PMID: 3022598


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