Estimation of insulin secretion using extracts of plasma from mice injected with anti-insulin serum: effects of arginine, glucose and anti-insulin serum

Abstract

Anti-insulin serum (AIS) injected intravenously into adult male mice was allowed to complex endogenous plasma insulin for a fixed time before blood samples were taken. In each plasma sample, insulin was separated from antibody using acid alcohol and the free insulin was estimated by radioimmunoassay. We consider AIS to be most useful for the estimations of in-vivo insulin secretion rates over the period 0·5–5 min after its injection. The lower limit is governed by the time required for mixing and complexing of endogenous insulin. The use of a short upper limit is because antibody complexed with antigen leaves plasma more rapidly than does free antibody, carrying antigen with it. Increases in insulin per ml plasma were appreciably greater in mice injected with glucose or l-arginine plus AIS than in mice injected with glucose or l-arginine only. Hence more realistic values for in-vivo insulin secretion rates may be obtained by the use of AIS to retain most insulin in plasma than by estimations of plasma insulin levels.