Localization of the Site of Action of Mercurial Diuretics by Stop Flow Analysis

¹ From the Department of Physiology, School of Medicine, University of Michigan, Ann Arbor, Michigan

Experiments utilizing the new technique of ‘stop flow’ analysis have been performed to localize the renal site of action of mercurial diuretics. Control ureteral occlusions were done on dogs after stabilization of mannitol osmotic diuresis. After release of occlusion and collection of samples, either thiomerin or meralluride (4–8 mg Hg/kg) was administered and a second occlusion performed forty minutes later. The mercurials caused at least a 50% reduction in the mass of water and sodium reabsorbed by the proximal tubule during the brief period of occlusion. These reductions were equivalent so that the sodium concentration of the proximal reabsorbate always remained plasma-like. The mercurials did not interfere with the ability of the distal tubule to lower urinary sodium concentration during the period of ureteral occlusion.