POTASSIUM SECRETION BY COLONIC MUCOSAL CELLS AFTER POTASSIUM ADAPTATION

Chronic K loading increases Na-K-ATPase specific activity in kidney tissue and suggest that this enzyme plays a role in renal K adaptation. Studies of fluid and electrolyte movement, potential difference (PD), and Na-K-ATPase were performed in colon and jejunum of the rat in order to further characterize the relationship of Na-K-ATPase to K secretion. Experimental rats fed a 2.6 meq K/gm diet for 7 days were compared to a control group fed 0.13 meq K/gm. In the colon, chronic K loading increased K secretion from 0.8 .+-. 0.2 to 3.9 .+-. 0.9 .mu.eq/min per g tissue (P < 0.01) and PD from 27 .+-. 5.0 to 54 .+-. 2.6 mV (P < 0.001), lumen negative, as Na-K-ATPase increased from 5.0 .+-. 0.5 to 11.4 .+-. 1.0 .mu.M Pi/mg protein per h (P < 0.001). There was no change in PD, K movement or Na-K-ATPase in the jejunum of K-loaded rats. Colonic movement of H2O, Na and Cl- was similar in the control and K-loaded rats. Increased Na-K-ATPase is associated with both increased PD and increased K secretion in the colon. Na-K-ATPase may be important in the control of transepithelial K movement.