Mechanism of enhanced transcellular potassium-secretion in man with chronic renal failure.

Previous studies from our laboratory demonstrated that net K secretion in human rectum was 2.5-fold higher in patients with chronic renal failure than in controls. The present study was performed to determine whether K secretion in human large intestine involves an active process and whether an active transport process accounts, at least in part, for the rise in net K secretion in patients with renal insufficiency. Studies were performed under conditions when net water and electrolyte transport approached zero, and the observed distribution of K and Na across the rectal mucosa was compared to expected equilibrium values. In control subjects an active transport of 27.6 +/- 2.6 mV was observed for K and 63 +/- 4.2 mV for Na. Similar values were demonstrated in patients with chronic renal failure. The results of these studies demonstrated that net secretion of K and absorption of Na are governed, at least in part, by active transport processes, and suggest that, since active K secretion is not impaired, the rise in net K secretion in patients with renal insufficiency is caused by active secretion as well as by passive driving forces.