Mouse glomerular endothelial cells have an insulin receptor

An insulin receptor was found on the surface of cloned mouse glomerular endothelial cells in vitro. Total specific binding was 2.5 ± 0.3%/10⁶ cells at 90 min and 22°C. Analysis according to Scatchard resulted in a curvilinear plot, with a kd for the high and low affinity sites estimated at 1.41 x 10^-10 and 8.2 x 10^-8 respectively. Insulin binding decreased following 12 hour exposure to 50 ng/ml of insulin suggesting that down regulation of the receptor had occurred, an effect which was reversible. Covalent crosslinking of the receptor to ¹²⁵I insulin revealed one band at M(r) 125,000 by SDS-PAGE which disappeared following preincubation with excess unlabeled insulin. Insulin was also able to stimulate phosphorylation of the β subunit. The characteristics of this insulin receptor appear very similar to that of endothelial cell types from other microvascular beds.