Effects of insulin on osteoblast and its post-receptor mechanism / 中国病理生理杂志

ABSTRACT

AIM: To study the effects of insulin on the proliferation and function of osteoblasts and the relationship between insulin post-receptor change in osteoblasts and osteoblastic cell growth.METHODS: The effects of different levels of insulin on osteoblasts were assessed by MTT colorimetry.Osteocalcin in medium was measured by RIM.IGF-1 mRNA expression levels were determined by RT-PCR.The concentrations of free IGF-1 protein in serum-free medium were measured by ELISA.In addition,the protein level and phosphorylated protein of P~(44/42)MAPK were determined by Western blotting analysis.RESULTS: Insulin enhanced the proliferation of osteoblasts,depending on its dose and exposure time.Insulin at concentration of 10~(-7) mol/L showed the strongest effect,and the action attained the plateau phase beyond 96 h.The best concentration that stimulated synthesis of osteocalcin by insulin was 10~(-7) mol/L.When the insulin concentration beyond 10~(-7) mol/L,the osteocalcin concentration was decreased.Exposure time had no effect on insulin-stimulated synthesis of osteocalcin of osteoblastic cells.When the concentration of insulin reaches 10~(-6) mol/L,the IGF-1 mRNA expression stimulated by insulin was also decreased.The concentrations of free IGF-1 protein in insulin-stimulated groups were all higher than that in control group(P0.05).Insulin acute stimulation rapidly induced the activity of tyrosine phosphorylation of P~(44/42)MAPK.The degree of tyrosine phosphorylation of P~(44/42)MAPK was increased step by step along with the increasing doses of insulin from 0 to 10~(-7) mol/L(P