[Kidney function and Na+-K+-ATPase and succinate dehydrogenase activity in the cells of the renal tubules of rats with constriction of the thoracic portion of the vena cava inferior].

Circulatory insufficiency in rats was induced by constriction of the thoracic portion of vena cava inferior. Two-three days after the operation renal function was studied and the activity of succinate dehydrogenase and Na+K+-ATPase in the cells of the renal tubules was determined cytochemically. On infusion of 0.9% NaCl solution into the stomach, the filtration in the "caval" rats did not change whereas the excretion of sodium and its concentration in the urine were much lower than in the sham operated rats. At the same time, the activity of Na+K+-ATPase and succinate dehydrogenase in the "caval" rats increased in the cells of the proximal tubule, diminished in Henle's loop, and remained unchanged in the cells of the distal convoluted tubule. Comparison of the results of functional and cytochemical study of the kidneys in caval rats allows the conclusion that intensified proximal reabsorption may be the main cause of antinatriuresis in these animals. The lesser load experienced by the distal segment promotes fuller reabsorption of sodium in this part of the nephron too.