Endothelin derived from the endothelial cells of microvessel is a potent vasoactive peptide, which has various physiologic actions in many internal organs. The fact that endothelin receptors are present on the osteoblastic cells suggests that endothelin play a role in bone metabolism. This study was done to study the effect of endothelin-1 on osteoblast and the combined effect of dexamethasone and endothelin-1 on osteoblast. Human osteoblasts isolated from ilium were cultured in DME/F12 medium, and divided into 5 groups; Group 1 (control), Group 2(10(-7)M endothelin-1), Group 3(10(-7)M endothelin-1+1:2500 monoclonal antibody), Group 4(10(-7)M dexamethasone+10(-7)M endothelin-1), and Group 5(10(-7)M dexamethasone). [3H]-thymidine uptake in groups was 23373.2+/-2722.4 cpm/well, significantly higher than that of control (P<0.05), and the increase was blocked by the addition of monoclonal antibody to endothelin(group 3). [3H]-thymidine uptake in groups adding steroid with or without endothelin was significantly lower than that of other groups (P<0.05). Group 2 showed marked increase in type I procollagen mRNA compared with other groups, but group 3 and 4 showed no significant effect on the expression of type I procollagen mRNA. In histochemical staining for alkaline phosphatase activity, the cells in groups with steroid were strongly positive in staining, large in size and looked well differentiated. Osteocalcin synthesis was also increased in groups with steroid treatment compared with other groups. This study demonstrated that endothelin-1 stimulated DNA synthesis and the expression of type I procollagen mRNA in human osteoblasts, and inhibited alkaline phosphatase activity, but had no significant effect on osteocalcin. Dexamethasone stimulated alkaline phosphatase activity and osteocalcin synthesis, and inhibited DNA synthesis but had no significant effect on the expression of type I procollagen mRNA. Dexamethasone masked the effect of endothelin-1 on human osteoblastic cells, and the effect of dexamethasone was predominant in the group of a combination of endothelin-1 and dexamethasone.
Alkaline Phosphatase ; Collagen Type I ; Dexamethasone ; DNA ; Endothelial Cells ; Endothelin-1 ; Endothelins* ; Humans ; Ilium ; Masks ; Metabolism ; Microvessels ; Osteoblasts* ; Osteocalcin ; Receptors, Endothelin ; RNA, Messenger