Sodium potassium ATPase activity in human rectal mucosa with and without renal insufficiency.

Studies in rats have shown that fecal potassium excretion and colonic mucosa Na-K-ATPase activity are elevated during dietary potassium loading and in chronic renal insufficiency. We studied Na-K-ATPase activity in human rectal mucosa in normal subjects as well as in patients with chronic renal insufficiency (creatinine clearance 2 to 72 mL/min). In normals, Na-K-ATPase activity was 4.34 +/- 0.83 mumol P/mg protein. After 2 weeks on a potassium intake of 300 mmol/d the mean activity did not differ significantly from the control value (2.49 +/- 1.30). In none of the patients with renal failure was Na-K-ATPase activity beyond the range found in the normal subjects, irrespective of serum potassium; the mean activity was 3.50 +/- 0.85. Like others, however, we found a two-fold increase in Na-K-ATPase activity in potassium loaded rats. Possible explanations for these differences are discussed.