Effect of the Antithyroid Drug Propylthiouracil on the Sodium Balance of Rats

Rats treated chronically with either propylthiouracil or thiouracil show a negative sodium balance, lose weight and eventually die if given a diet deficient in sodium. When the diet is deficient in both sodium and potassium, goitrogen-treated rats lose more sodium and less potassium than untreated controls, with resultant high urinary Na/K ratios. The high urinary Na/K ratio is typical of animals with adrenocortical deficiency. Indeed, goitrogen-treated rats, given a choice between water and NaCl solution to drink, manifest a spontaneous appetite for NaCl solutions which is similar in character to that seen in adrenalectomized rats. The possibilities exist that these drugs interfere with: (a) renal production of renin, which is now known to stimulate adrenal secretion of aldosterone; (b) adrenal cortical secretion of aldosterone; and (c) utilization of aldosterone by the kidney tubule. The present experiments do not indicate which one of the above, if any, is responsible for the increased sodium loss of goitrogen-treated rats.