Post-obstructive nephropathy in the rat: relationship between NA-K-ATPase activity and renal function.

Na-K-ATPase activity and renal function were compared in rats studied after relief of 24 h of unilateral or bilateral ureteral ligation (UUL or BUL), that is, in the absence or presence of post-obstructive diuresis. Na-K-ATPase activity in the outer medulla of the rat kidney after relief of UUL was not significantly altered immediately but was markedly reduced 1 and 3 days post-obstruction. The decrease in medullary Na-K-ATPase activity was not significantly different from that observed after relief of BUL. These results indicate that decreased Na-K-ATPase activity in the post-obstructive kidney is not responsible for post-obstructive diuresis and is not due to uremia, but is a local phenomenon which is probably secondary to altered renal structure or function. It may be due to decreased filtered sodium load or direct tubular damage, but other data suggests that the decreased medullary solute concentration gradient in the post-obstructive kidney (UUL or BUL) may influence Na-K-ATPase activity which, in turn, contributes to the decreased ability to conserve sodium and water.