Mouse Glomerular Endothelial Cells Have an Insulin Receptor

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Abstract
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.degree. C. Analysis according to Scatchard resulted in a curvilinear plot, with a kd for the high and low affinity sites estimated at 1.41 .times. 10-10 and 8.2 .times. 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 Mr 125,000 by SDS-PAGE which disappeared following preincubation with excess unlabeled insulin. Insulin was also able to stimulate phosphorylation of the .beta. subunit. The characteristics of this insulin receptor appear very similar to that of endothelial cell types from other microvascular beds.