INCREASED WATER EXCHANGE IN RATS TREATED WITH ANTITHYROID DRUGS

¹ Department of Physiology, University of Florida, College of Medicine, Gainesville, Florida

Treatment of either intact or hypophysectomized rats with the antithyroid drugs, propylthiouracil, thiouracil and methimazole, is accompanied by an increased water intake and urinary output. The increased water intake does not appear to be the result of an increased "thirst" drive as assessed by drinking response either to dehydration or to Pitressin injection. It seems likely that the increased water intake observed is secondary to the increased urinary output since both intact and hypophysectomized rats, treated with propylthiouracil, manifest a decreased urinary concentrating ability after either dehydration or Pitressin administration. The latter may be due both to a reduced response of kidneys to endogenous antidiuretic hormone and to diuretic properties of the antithyroid drugs.