Insulin binding to plasma membranes

Abstract

Insulin binding to plasma membranes from rat epididymal fat pad, liver, brain and human red blood cell membranes was estimated by the displacement of [ 125I]-insulin by native insulin. Membranes isolated from rat epididymal fat pad bound more insulin than rat liver plasma membranes. Rat brain and human red cell membranes bound essentially no insulin. Glucose bound to fat pad membranes and this binding was decreased by insulin. The binding of labeled insulin was reduced in proportion to the relative concentration of labeled and unlabeled insulin. Maximum insulin binding required the presence of Na +, K + and glucose. The binding of insulin was not altered by the insulin derivatives: sulfonated B chain, reduced-reoxidized insulin and oxidized B chain. The binding of insulin was inhibited in proportion to the concentration of added guinea pig anti-insulin serum. An increase in insulin binding was obtained following treatment of fat pad membranes with either phospholipase C or trypsin.