The effect of insulin-like growth factor II on glucose uptake and metabolism in rat skeletal muscle in vitro.

The effect of insulin-like growth factor II (IGF II) on the rates of lactate formation, glycogen synthesis and glucose transport in the presence of a range of concentrations of insulin were investigated using an isolated preparation of rat skeletal muscle. IGF II, at a concentration of 65 ng/ml, caused a small but significant increase in the rates of these processes at a basal physiological insulin concentration (10 muunits/ml), but was without effect in the presence of 1, 100, 1000 or 10,000 muunits of insulin/ml. Hence IGF II increased the insulin sensitivity of this tissue. This effect was removed if the incubation medium was supplemented with an equimolar concentration of IGF binding protein 1 (BP1). It is suggested that changes in the concentration of IGF II and/or BP1 may regulate glucose uptake and metabolism in skeletal muscle and have physiological significance in the control of blood glucose level.