EFFECT OF MERALLURIDE ON DISTAL NEPHRON TRANSPORT OF SODIUM, POTASSIUM AND CHLORIDE

¹ Department of Physiology, University of Kansas School of Medicine, Kansas City, Kansas

The stop flow technique was employed to investigate the effects of meralluride upon sodium, chloride and potassium transport mechanisms in distal segments of the dog nephron. Sodium reabsorption in the distal nephron was inhibited by meralluride. This effect is enhanced with increasing plasma sodium concentrations. It is not an artifact of increased plasma or free flow urine sodium concentrations. Chloride reabsorption was also inhibited by meralluride. However, no inhibition was seen in the presence of the impermeant sulfate anion. It is concluded that meralluride primarily inhibits sodium reabsorption, resulting in an indirect effect upon chloride reabsorption. In control experiments, meralluride depressed potassium clearance but did not inhibit potassium secretion during stop flow. However, in dogs chronically loaded with potassium and in dogs given acetazoleamide, meralluride did inhibit potassium secretion during stop flow. In dogs depleted of potassium, the drug tended to stimulate potassium secretion during stop flow. This latter effect may be due to an increase in the supply of exchangeable sodium.