INSULIN-RECEPTOR BINDING IN ADIPOCYTES

Publisher Summary This chapter discusses how insulin interacts with receptors in rat adipocytes and how it elicits one of its important effects: the increase in the permeability of the plasma membrane to glucose. It discusses three processes: (1) the receptor binding of 125 I-labelled insulin that is used as a tracer for insulin, (2) the effect of insulin on transmembrane transport of 3-O-methylglucose; this glucose analog is used because it is not phosphorylated and metabolized, and (3) the degradation of insulin that occurs in two ways in a suspension of rat adipocytes in vitro . Receptor-bound insulin is degraded in adipocytes incubated at near-physiological temperature and pH. The binding of insulin to its receptor is, therefore, not a bimolecular reversible reaction. Insulin in a very high concentration requires about 50 seconds toincrease the permeability of adipocytes to methylglucose. Insulin increases the maximal transport velocity possibly by increasing the number of available carriers.