Abstract
We investigated the effect of streptozotocin-induced diabetes on 125I-epidermal growth factor (125I-EGF) binding to microsomal membranes from rat liver and phosphorylation of its receptors. The binding of EGF to hepatic membranes from diabetic animals was found to be significantly low, about 60% of the control level. The results from Scatchard analysis of binding data and affinity labeling of EGF receptors clearly showed that the decrease in binding of EGF to membranes from diabetic animals was due to a decrease in the number of EGF receptors (MW= 170, 000). Treatment of diabetic animals with insulin restored the number of receptors to the control level. EGF stimulated the phosphorylation of its receptors in hepatic membranes. The rates of basal and EGF-stimulated phosphorylation of EGF receptors in control, diabetic and insulin-treated dibetic rats were almost parallel with the changes in the number of receptors. These results suggest that insulin deficiency in vivo causes a decrease in the number of hepatic EGF receptors, and probably affects the functions of the liver.
