Hepatic extraction of plasma immunoreactive glucagon components. Predilection for 3500-dalton glucagon metabolism by the liver

Abstract

This study examines quantitatively the extraction of plasma immunoreactive glucagon (IRG) components by the liver. It was shown that the liver has a predilection for removal of the 3500-dalton biologically active IRG component with virtually no extraction of the other IRG fractions. Hepatic extraction of whole plasma IRG was 25.2 +/- 2.5%. Analysis of the hepatic extraction of the four plasma immunoreactive components, separated by gel filtration, revealed variable but quantitatively insignificant extraction of all components other than the 3500-dalton fraction, which was 33.4 +/- 3.2% (P less than 0.001). Hepatic extraction of whole plasma IRG was significantly less than that of the 3500-dalton component during periods of basal glucagon secretion when IRG fractions other than the 3500-dalton fraction contribute substantially to the whole plasma IRG level. However, during periods of stimulation of glucagon secretion by arginine or arginine plus cholecystokinin-pancreozymin, when the 3500-dalton component accounts for virtually all of the whole plasma IRG level, hepatic extraction of whole plasma IRG was similar to that of the 3500-dalton fraction.