EFFECT OF PROTEIN RESTRICTION ON MESSENGER-RNA OF INSULIN-LIKE GROWTH-FACTOR-I AND INSULIN-LIKE GROWTH FACTOR-BINDING PROTEINS IN LIVER OF OVARIECTOMIZED RATS

Effects of dietary protein restriction and ovariectomy on plasma conce ntrations and hepatic messenger RNA (mRNA) of insulin-like growth fact or-I (IGF-I) and insulin-like growth factor binding proteins (IGFBP) w ere investigated in young female rats. Ovariectomy increased plasma IG F-I concentration in rats fed on either a 50 g casein/kg diet (protein -restricted diet) or a 200 g casein/kg diet (control diet), but it inc reased IGF-I mRNA in liver only in the rats fed on the control diet. O n the other hand, by Western ligand blot analysis, we observed that ov ariectomy increased plasma IGFBP-3 concentration, and decreased plasma IGFBP-4 concentration. Ovariectomy did not affect IGFBP-1 and IGFBP-2 mRNA in liver, but dietary protein restriction significantly increase d them, which may correspond to their plasma concentrations. The prese nt results show that ovarian hormones and dietary protein content affe ct the plasma concentrations of IGF-I, IGFBP-3 and IGFBP-4 and hepatic mRNA of IGF-I, IGFBP-1, IGFBP-2, IGFBP-3 and IGFBP-4 in different man ners.