The effect of insulin on glucose transport in rabbit erythrocytes and reticulocytes

Insulin binding and 3-0-Methylglucose transport have been studied in erythrocyte- and reticulocyte-enriched fractions of blood cells in order to determine if the increased number of insulin binding sites in reticulocytes is associated with a glucose transport response to insulin. In these experiments rabbit reticulocytes demonstrate an eightfold increase in total insulin receptors when compared to erythrocytes. Glucose transport activity in the erythrocyte has a K_m of 3.2 mM. Reticulocytes demonstrate a saturable glucose transport activity of lower affinity, K_m 18.9 mM. Neither the erythrocyte, nor the reticulocyte glucose transport activity, was capable of an increased response to insulin. The low affinity glucose transport activity in reticulocytes could allow a fourfold increase in facilitated glucose transport at supraphysiological glucose concentrations that might occur in poorly controlled diabetes mellitus.