Triiodothyronine stimulates45Ca-accumulation via synthesis of insulin-like growth factor-I in cultures of osteoblast-like cells

Abstract

We examined the effects of triiodothyronine (T3) on45Ca-accumulation into extracellular matrix in osteoblast-like MC3T3-El cells cultured for 7-week period, which was considered to be long enough to develop calcification. T3 increased45Ca-accumulation into sodium dodecyl sulfate-insoluble, EDTA-extractable materials cultures of MC3T3-El cells in a dose-dependent manner in the range between 10 pM and 10 nM. Contrary to the stimulatory effect on45Ca-accumulation, T3 inhibited DNA synthesis in MC3T3-El cells dose dependently between 10 pM and 10 nM. T3 stimulated the secretion of insulin-like growth factor-I (IGF-I) dose dependently between 0.1 nM and 10 nM in MC3T3-El cells cultured for 7 weeks. Antibodies to IGF-I suppressed the45Ca-accumulation induced by T3 almost to the control level. These results strongly suggest that T3 stimulates45Ca-accumulation via synthesis of IGF-I in osteoblast-like cells.