Pancreatic hormone receptors on islet cells

Endocrinology. 1985 Sep;117(3):841-8. doi: 10.1210/endo-117-3-841.

Abstract

To assess whether islet cells are equipped with recognition units which allow an intra-islet regulation via released hormones, the presence of insulin and glucagon receptors is investigated on purified pancreatic A and B cells. Mono-[125I]glucagon is shown to bind specifically to islet B cells, with similar binding characteristics as in isolated hepatocytes but involving less receptors per cell (2.10(4) per B cell vs. 8.10(5) per liver cell). Binding is half-maximally displaced by 5.10(-9) M glucagon, a concentration known to induce half-maximal biological effects in isolated B cells. These results are compatible with a regulatory role of glucagon in the insulin release process. No specific binding of [125I]tyr-A14-insulin is detected on pancreatic A cells. In order to increase receptor assay sensitivity, [123I]tyr-A14-insulin is prepared with at least 5-fold higher specific activity. Its validity for in vitro receptor analysis is demonstrated in IM-9 lymphocytes, where insulin binding is detectable down to 10(4) cells/ml. However, no insulin-binding sites are identified on pancreatic A cells, even at 10(6) cells/ml. If isolated A cells contain high affinity insulin receptors, their number should be inferior to 400 per cell, which is 50- to 500-fold lower than in classical insulin target cells. These findings explain the insensitivity of the glucagon release process to acute exposure to insulin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Binding, Competitive
  • Cell Line
  • Chromatography, High Pressure Liquid
  • Glucagon / metabolism
  • Insulin / analogs & derivatives
  • Insulin / metabolism
  • Islets of Langerhans / metabolism*
  • Kinetics
  • Lymphocytes / metabolism
  • Male
  • Rats
  • Receptor, Insulin / metabolism*
  • Receptors, Cell Surface / metabolism*
  • Receptors, Glucagon

Substances

  • Insulin
  • Receptors, Cell Surface
  • Receptors, Glucagon
  • insulin, 3-iodo-Tyr(A14)-
  • Glucagon
  • Receptor, Insulin