ACUTE EFFECTS OF THE ADMINISTRATION OF VASOPRESSIN DURING WATER DIURESIS IN THE DOG*

Abstract

Vasopressin, 300 mU prime and 30 mU/kg/hour, was infused into conscious dogs during water diuresis, and frequent urine samples collected via catheter up to 120 minutes thereafter. A maximal concentration of nonurea solute (NUS) was usually attained in 20-30 minutes. In the initial 10 minutes after vasopressin, concentration of NUS rose more rapidly than that of urea, indicating movement of the latter out of the tubular lumen. Low protein diets given for 5 days had no effect on the NUS concentration achieved. Similarly, dehydration did not result in an augmentation of NUS concentration over that observed during water diuresis plus vasopressin in the same animals. These data suggest that prolonged vasopressin action, either by infusion or by endogenous secretion, does not augment the medullary Na gradient above that observed by acute hormone administration in hydrated animals. A direct correlation between the rate of inulin clearance and maximal NUS concentration was observed in multiple experiments on two dogs.