Acute actions of insulin-like growth factor II on glucose metabolism in adult rats.

The metabolic potency of recombinant human insulin-like growth factor II was studied in anaesthetized adult rats by obtaining dose-response curves for the hypoglycaemic action and for the stimulation of glucose metabolism during euglycaemic clamping. Compared to insulin, about 50 times higher doses of insulin-like growth factor II were required to result in identical in vivo responses, with half-maximally effective serum concentrations for the stimulation of glucose disposal during clamp studies of about 0.8 and 50 pmol/ml, respectively. A similar difference in potency was observed for the dose-dependent stimulatory actions on glucose metabolism in individual target tissues. Half-maximally effective serum concentrations in the range of 0.8 to 3.0 pmol/ml for insulin and of 40 to 70 pmol/ml for insulin-like growth factor II were seen to be required for 2-deoxyglucose uptake, glycogen formation in skeletal muscle and lipogenesis in epididymal fat. Maximal responses were identical with both peptides. These data suggest that in vivo acute metabolic actions of insulin-like growth factor II on carbohydrate metabolism occurred through insulin receptors.