Insulin and insulin-like growth factor I binding to cultured rat glomerular mesangial cells

Endocrinology. 1988 Nov;123(5):2432-9. doi: 10.1210/endo-123-5-2432.

Abstract

The potential effects of insulin and insulin-like growth factor I (IGF-I) on mesangial cell (MC) metabolism and growth were examined. Radiolabeled insulin or IGF-I were incubated with cell membranes from rapidly proliferating (subconfluent) or nonproliferating (confluent) MC in the presence of increasing concentrations of unlabeled heterologous and homologous ligands (0-10(-6) M). Insulin binding to MC was specific and saturable, with Scatchard analysis of binding data showing the characteristic curvilinear plot. The predicted insulin binding maximum of 4.2 X 10(-12) M/100 micrograms protein for a theoretical high affinity site was consistent with a relatively low density of receptors, which were the same in proliferating and nonproliferating cell preparations. Specific binding of IGF-I to MC was also demonstrated. Binding data for membranes from proliferating cultures generated a linear Scatchard plot, which predicted a binding maximum of 3.5-9.7 X 10(-11) M/100 micrograms protein and a Kd of 2.0-3.2 X 10(-9) M. In contrast, membranes from nonproliferating cultures had no demonstrable specific binding of IGF-I. Covalent cross-linking of radiolabeled IGF-I to membranes from subconfluent cells demonstrated specific binding to a 145K membrane protein. A 95K membrane protein from a partially purified receptor preparation demonstrated autophosphorylation when incubated with 5 X 10(-9) M IGF-I. Incubation of MC with 10(-9) M IGF-I doubled cellular growth rates, an effect that could be duplicated only with high concentrations (10(-6) M) of insulin. These observations indicate that MC express predominantly receptors for IGF-I, and that growth stimulatory effects of physiological concentrations of IGF-I and pharmacological concentrations of insulin are probably mediated through the IGF-I receptor.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Affinity Labels
  • Animals
  • Cell Division
  • Cell Membrane / metabolism
  • Cells, Cultured
  • Cross-Linking Reagents
  • Glomerular Mesangium / metabolism*
  • Insulin / metabolism*
  • Insulin-Like Growth Factor I / metabolism*
  • Male
  • Phosphorylation
  • Rats
  • Rats, Inbred Strains
  • Somatomedins / metabolism*
  • Succinimides

Substances

  • Affinity Labels
  • Cross-Linking Reagents
  • Insulin
  • Somatomedins
  • Succinimides
  • Insulin-Like Growth Factor I
  • disuccinimidyl suberate