Effects of MK-196 on urate and electrolyte excretion in the rat.

Clearance and micropuncture techniques were used to evaluate the effects of MK-196 on uric acid and electrolyte excretion by the rat kidney. The urinary excretion of sodium, uric acid, calcium and magnesium increased significantly following MK-196 administration. The major site of action with respect to sodium reabsorption was in the ascending limb of Henle's loop as revealed by depression of both free-water clearance and reabsorption. By contrast, microinjection studies with [2-14C]-urate revealed the major site of altered urate absorption to be in the proximal convoluted tubule, a site where sodium and water reabsorption was unchanged.