Characterization of the renal handling of vasopressin in the dog by stop-flow analysis.

The stop-flow technique has been used to characterize the renal handling of vasopressin in the anesthetized dog. To facilitate the measurement of vasopressin in small urine samples by a specific RIA, the plasma vasopressin concentration was elevated by the iv infusion of arginine vasopressin. Under control conditions, the urinary clearance of vasopressin did not differ significantly from the glomerular filtration rate. The data obtained with the stop-flow technique indicate that vasopressin was reabsorbed from or degraded in the proximal nephron and secreted into the distal nephron. Thus, vasopressin excreted in the final urine is the result of glomerular filtration (which is limited to the extent that vasopressin is bound to plasma proteins), proximal reabsorption or degradation of filtered vasopressin, and distal secretion of vasopressin. It is likely that the tubular secretion of vasopressin is an important component of the renal organ clearance of this hormone.