Summary
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 × 109 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 × 109 erythrocytes (P < 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 < 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.
Key-Words
Insulin Receptor
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Erythrocyte
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Down-regulation
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Counterregulation
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Euglycaemia
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Hypoglycaemia
