The Erythrocyte Insulin Receptor Response to Insulin Induced Hypoglycaemia

The response of the erythrocyte insulin receptor to a prolonged intravenous infusion of insulin has been measured in normal individuals during hypoglycaemia and when hypoglycaemia was prevented by the concurrent infusion of glucose. When euglycaemia was maintained, mean (+/- S.D.) specific insulin binding following the 5 hour insulin infusion was unchanged (6.9 +/- 2.1 to 6.65 +/- 2.2% bound per 2.25 X 10(9) erythrocytes). In the presence of mild hypoglycaemia, mean (+/- SD) specific insulin binding rose from 6.6 +/- 2.3 to 7.6 +/- 2.5% bound per 2.25 X 10(9) erythrocytes (P less than 0.01), after 5 hours. This increase was due to increased receptor affinity. It was not correlated with the increase in the concentration of any individual counter-regulatory hormone. Initial insulin receptor binding correlated strongly with the subsequent decline in plasma glucose concentration (r = 0.9527; P less than 0.01). Thus, acute hyperinsulinaemia, when associated with hypoglycaemia, does not result in downregulation of insulin receptors on erythrocytes but rather results in increased receptor binding. Consequently, the insulin receptor may not play an active role in protecting the individual against acute hypoglycaemia.