INSULIN-LIKE GROWTH-FACTOR-I ENHANCES THE FORMATION OF TYPE-I COLLAGEN IN HYDROCORTISONE-TREATED HUMAN OSTEOBLASTS

We have studied the effect of insulin-like growth factor I (IGF-I) on the formation of osteocalcin and type I collagen in isolated human ost eoblasts. IGF-I at and above 0.1 nM stimulated the formation of type I collagen as measured by the type I procollagen carboxyterminal peptid e (PICP), in human osteoblasts, incubated for 72 hrs in serumfree cond itions. The secretion of osteocalcin was not affected by IGF-I while 1 ,25(OH)(2), vitamin D-3 significantly enhanced the formation of osteoc alcin. When human osteoblast-like cells were incubated with hydrocorti sone (1 mu M), a significant decrease in the release of both PICP and osteocalcin was seen. Addition of IGF-I to human osteoblasts also trea ted with hydrocortisone normalized the PICP-formation but did not affe ct the suppressed osteocalcin-formation. These data indicate that IGF- I reverses selective effects of hydrocortisone on bone.