Hepatic elimination of endogenous gastrin in pigs

To assess hepatic elimination of gastrin, concentrations of gastrin were determined radioimmunochemically in plasma samples collected simultaneously in six pigs from the portal vein, hepatic vein, and a peripheral artery before and after stimulation of the antrum with meat extract. The portal plasma flow and the total plasma volume were measured. During meat extract stimulation the antral release of gastrin increased significantly (p less than 0.05), from 15.9 +/- 3.4 ng/min to 35.6 +/- 5.4 ng/min, and the hepatic elimination increased significantly (p less than 0.05), from 10.4 +/- 2.8 ng/min to 25.5 +/- 5.9 ng/min (mean +/- S.E.M., six pigs). The artery to mesenteric vein concentration ratio was 1.03 +/- 0.05 in the basal and 0.97 +/- 0.10 in the stimulated period, indicating neither release nor uptake of gastrin in the intestines of five pigs. Hepatic elimination of gastrin was roughly proportional to the gastrin concentrations in portal venous plasma. The mean hepatic plasma clearance of gastrin was 148 +/- 26 ml/min and the total body clearance 268 +/- 43 ml/min. Thus extrasplanchnic gastrin removal accounted for half of total body elimination. It is concluded that in anesthetized pigs the "first-pass" effect on portal gastrin content makes the liver one of the important sites for elimination of endogenous gastrin.