INDUCTION OF INSULIN-LIKE GROWTH-FACTOR RECEPTOR (IGF IR) MESSENGER-RNA LEVELS BY LOW-DENSITY LIPOPROTEINS

Smooth-muscle cell (SMC) proliferation is a major step in the developm ent of atherosclerotic lesions. Insulin-like growth factor (IGF I) is a progression factor for smooth muscle cells. We have previously repor ted an increased level of expression of insulin-like growth factor I r eceptor (IGF IR) gene in SMC of atherosclerotic plaques of rabbit aort as. Here we report that low density lipoproteins (LDL) produced an alm ost twofold increase in the steady state levels of IGF I R mRNAs in cu ltured smooth muscle cells of the rat aortic cell line A10. The increa se was specific for LDL and was not detected in the presence of high d ensity lipoproteins (HDL). These results indicated that increased IGF IR mRNA levels may be related to the genesis of the atherosclerotic le sion and suggested a new explanation for the atherogenic effect of LDL . (C) 1996 Academic Press, Inc.