Induction of insulin-like growth factor receptor (IGF IR) mRNA levels by low density lipoproteins.

Smooth-muscle cell (SMC) proliferation is a major step in the development of atherosclerotic lesions. Insulin-like growth factor (IGF I) is a progression factor for smooth muscle cells. We have previously reported an increased level of expression of insulin-like growth factor I receptor (IGF IR) gene in SMC of atherosclerotic plaques of rabbit aortas. Here we report that low density lipoproteins (LDL) produced an almost twofold increase in the steady state levels of IGF I R mRNAs in cultured smooth muscle cells of the rat aortic cell line A10. The increase was specific for LDL and was not detected in the presence of high density lipoproteins (HDL). These results indicated that increased IGF IR mRNA levels may be related to the genesis of the atherosclerotic lesion and suggested a new explanation for the atherogenic effect of LDL.