Renal Sodium- and Potassium-Activated Adenosine Triphosphatase Deficiency During Post-obstructive Diuresis in the Rat

Renal function studies and tissue enzyme analysis were carried out in rats with bilateral ureteral ligation (24 h) and after relief of obstruction at intervals of 2 h, 24 h, 3 days, and 7 days. A persistent decrease in glomerular filtration rate and in tubular reabsorption of sodium, solute, and water was noted at each interval after relief of obstruction. Renal sodium- and potassium-activated adenosine triphosphatase (Na–K-ATPase) activity was unchanged in kidneys obstructed for 24 h, but enzyme activity was decreased in the outer medulla of the kidney and, less often, in the renal cortex, at each interval studied during the post-obstructive period. Magnesium-dependent adenosine triphosphatase (Mg-ATPase) activity was not changed in any of the groups. In the post-obstructive kidney (24 h, 3 days, and 7 days) there was a significant correlation between the decrease in outer medullary Na–K-ATPase activity and the changes in filtered sodium load, tubular reabsorption of sodium, and urine osmolality. A deficiency of renal Na–K-ATPase could be important in the pathogenesis of post-obstructive natriuresis and diuresis.