THE INFLUENCE OF VASOPRESSIN ON THE PERMEABILITY OF THE MAMMALIAN COLLECTING DUCT TO UREA*

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Abstract
The effect of vaso-pressin on the relative concentrations of urea within the renal medulla and within the urine has been determined in a set of paired steady state experiments in dogs. In every experiment a higher tissue to urine concentration ratio for urea was observed during vasopressin administration than during water diuresis. In additional studies the rate of appearance of intravenously injected C14 urea in the renal medulla was enhanced by vasopressin, suggesting that vasopressin increases the rate of turnover of urea within the renal medulla. Similarly, equilibration of labeled urea between urine and renal papilla was more rapid in the presence of vasopressin. The data indicate that the rate of movement of urea from the collecting duct lumen to the peritubular fluid is augmented by the action of vasopressin. These results are interpreted to indicate a direct effect of vasopressin on the permeability of the collecting duct epithelium.