Hepatic and renal clearance of vasopressin from plasma of dogs

Abstract

The fraction of vasopressin removed from portal venous plasma by the liver (hepatic portal extraction ratio) was estimated in conscious, hydrated female dogs. Antidiuretic responses to physiological doses of beef Pitressin (Parke, Davis) given as 5-min infusions via a splenic vein catheter were compared with responses to the same dose infused via a foreleg vein. The fraction of vasopressin removed during passage through the left kidney was estimated in experiments of analogous design. Antidiuretic responses of the right kidney to physiological does given as 5-min infusions via a catheter implanted transaortically in the left renal artery were compared with responses of the right kidney to the same dose given via a foreleg vein. Infusions were given by the alternate routes at hourly intervals. The hepatic portal extraction ratio for vasopressin averaged 12%. The renal extraction ratio averaged 25%. The renal extraction ratio, estimated by bioassay of arterial and renal venous plasma, was somewhat smaller (20%) in anesthetized dogs in which the concentration of vasopressin in the plasma was raised to unphysiologically high values by a constant infusion of beef Pitressin. From measurements of plasma flow through these organs and the extraction ratios, the clearances of vasopressin in the liver and both kidneys were calculated. The respective estimates, expressed as percent of plasma volume cleared per minute, were: hepatic, 4.6; renal (physiological plasma concentrations), 9.4; and renal (high plasma concentrations), 5.8.