Functional significance of Na- K-ATPase in the kidney: effects of ouabain inhibition.

TORRETTI, JORGE, ERNESTO HENDLER, EDWARD WEINSTEIN, ROBERT E. LONGNECKER, AND FRANKLIN H. EPSTEIN. Functional sign@ance of NaK-A Vase in the kidney: e$ect.s of ouabain inhibition. Am. J. Physiol. 222(6): 1398-1405. 1972.-Infusions of ouabain directly into the renal artery of the dog produced substantial inhibition of renal Na-K-ATPase activity, which was almost complete in some experiments. The amount of ouabain bound to renal tissue in vivo was stoichiometrically related to the inhibition of NaK-ATPase discerned in tissue homogenates. Concentrating and diluting ability were impaired. The reduction in fractional reabsorption of sodium produced by ouabain was greatly influenced by preliminary maneuvers designed to vary the distribution of tubular absorption between proximal and distal tubules. Ethacrynic acid did not produce further diuresis in a kidney already maximally blocked with ouabain. The results are consistent with the hypothesis that NaK-ATPase plays a prominent role in sodium transport in the thick ascending limb of the loop of Henle and the distal convolution and plays a lesser one in the proximal tubule.