STUDIES ON TISSUE UPTAKE OF INSULIN IN MAN USING A DIFFERENTIAL IMMUNOASSAY FOR ENDOGENOUS AND EXOGENOUS INSULIN*

Abstract

The separate measurement of beef and human insulin in plasma in man after beef insulin administration is based on differences in species specificity shown by human and guinea pig antibeef insulin antisera. Direct measurements of the hepatic uptake of endogenous and beef insulin in four subjects with portacaval anastomoses or extrahepatic portal blocks shows that, in man, the liver is capable of removing 20 to 50% of the insulin passing through it for periods of over one hour. The mean proportion of arterial insulin removed by the liver, reflected by the ratio; arterio-hepatic venous difference in insulin concentration/arterial insulin concentration, was similar for endogenous (mean, 0.40) and exogenous (mean 0.42) insulin. The mechanism for hepatic beef insulin capture behaved as a first order system and was not saturated by arterial plasma beef insulin levels of 250 [mu]U per ml. A peripheral insulin uptake of endogenous and exo -genous insulin, of lesser degree and more variable than the hepatic insulin uptake, is also demonstrated.