Renal potassium adaptation: Na-K-ATPase activity along the nephron after chronic potassium loading

Abstract

To identify nephron sites where renal K adaptation takes place, Na-K-ATPase was measured with a micromethod along the nephron of K-loaded mice. A possible role of aldosterone in this process was evaluated in K-loaded animals treated concurrently with pharmacologic doses of spironolactone. Animals fed a K-enriched diet for at least 2 wk excreted .apprx. 90% of ingested K in the urine, and fractional clearance averaged 87 .+-. 8%, compared with 13 .+-. 2% in controls. Na-K-ATPase activity/mm tubule length increased by 225% in the cortical collecting tubule and by 177% in the medullary collecting tubule, but was not substantially affected in other nephron segments. Stimulation of Na-K-ATPase was identical in the cortical collecting tubule of K-loaded mice treated with spironolactone. Chronic K loading in the mouse results in an adaptive increase in Na-K-ATPase in the collecting tubule and suggest that this nephron segment is the major site of K adaptation in this species. This effect appears to be independent of aldosterone.