Potassium transport across renal distal tubules during acid-base disturbances.

~MALNIC, GERHARD, MARGARIDA DE MELLO AIRES, AND GERHARD GIEBISCH. Potassium transport across renal distal tubules during acid-base disturbances. Am. J. Physiol. 221(4) : 1192-1208. 197 1 .-Free-flow samples of tubular fluid (TF) were collected from superficial nephrons of rat kidneys for the analysis of potassium (K), pH, bicarbonate and inulin-W. Rats were subjected to metabolic or respiratory acidosis and alkalosis, to combinations of these acid-base disturbances, and to acute K loading. 1) The distal tubular epithelium is the main site where alterations in the acid-base status effect changes in K transport, 2) Distal tubular K secretion is reduced in acute metabolic and respiratory acidosis despite a sharp increase in plasma K, whereas metabolic and respiratory alkalosis enhance distal K secretion despite a fall in plasma K levels. 3) An increase in distal intratubular pH is associated with increasing potassium secretion. 4) Intracellular acidification, independent of intratubular pH, reduces distal K secretion. 5) K entry into the distal tubule proceeds down an electrochemical potential gradient; and 6) no evidence was obtained of a consistent reciprocal relationship between rates of distal tubular K and hydrogen secretion.