Improved insulin receptor assay: effects of an antidiabetic sulphonylurea on liver membrane insulin receptors from obese hyperglycaemic mice.

1 A simple assay of liver membrane insulin receptors is described, under conditions which apparently stabilized the insulin-receptor complex. The receptor population was measured in the presence of physiological doses of radioactive hormone under conditions which minimized negative co-operativity effects. 2 Equilibrium between receptor and hormone was attained in vitro within 60 min of incubation time at 13 degrees C with no apparent loss of binding sites after 3 h of incubation. 3 Liver membranes from lean mice possessed 8.8 times the receptor number per mg membrane protein measured in membranes from obese hyperglycaemic (ob/ob) littermates. After treatment of ob/ob mice with ARDF-26 (Gliquidon; Boehringer Ingelheim Ltd) the concentration of liver membrane insulin receptors was increased 5 fold.