title: Does insulin down-regulate its own receptor on erythrocytes in vitro?
abstract: The purpose of this study was to examine the in vitro effect of insulin on its own receptors on erythrocytes. Whole blood from 6 fasting normal and 6 diabetic (type II) subjects was incubated without or with exogenous insulin for 5 hours. The insulin binding to erythrocytes was then evaluated. At a tracer concentration, the percent 125I-insulin specifically bound amounted to 8.6 +/- 0.59% and 8.1 +/- 0.41% in fasting normal subjects and type II-diabetics, respectively. In contrast to in vivo studies, supraphysiologic insulin concentrations in the incubation medium did not alter significantly the insulin binding process. Thus, in vitro we could not demonstrate a down regulation of insulin receptor binding. It is likely that factors other than insulin are involved in the short-term regulation of insulin receptor affinity in man.
mesh_terms: D004912:Erythrocytes / Q000032:analysis*; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology*; D008297:Male; D011972:Receptor, Insulin / Q000032:analysis / Q000187:drug effects*
chemical_list: D007328:Insulin; D011972:Receptor, Insulin