INFLUENCE OF 17β-ESTRADIOL (E₂) ON EFFECTS OF 1,25-DIHYDROXYVITAMIN D3 ［1,25(OH)₂D₃］ IN HUMAN OSTEOBLAST-LIKE CELL LINE TE85

AIM　Human osteoblast-like cell line TE85 was used to examine the effects of 1,25(OH)₂D₃ and 1,25(OH)₂D₃ with E₂. METHODS　³H-thymidine incorporation method was used for cell proliferation assay and ³H-proline incorporation for collagen synthesis assay. Alkaline phosphatase (ALP) activity was measured by ultraviolet spectrophotometry and bone gla-protein (BGP) content by radioimmunoassay. RESULTS　Exposure to 0.5～5 nmol.L^-1 of 1,25(OH)₂D₃ for 96 h, the ³H-thymidine incorporation was depressed in a concentration-dependent manner. But, exposure to 5 nmol.L^-1 1,25(OH)₂D₃ for 72 h, the ALP activity increased by 29.7%, and ³H-proline incorporation enhanced by 144.7%. Between 0.5～5 nmol.L^-1, the effects of 1,25(OH)₂D₃ on ³H-proline incorporation were in concentration-dependent fashion. In the presence of 1 nmol.L^-1 E₂, the actions of 1,25(OH)₂D₃ on collagen synthesis and BGP secretion augmented compared with 1,25(OH)₂D₃ alone. CONCLUSION　1,25(OH)₂D₃ exhibited potent effects on bone formation, and these effects were augmented in the presence of E₂. E₂ modulated 1,25(OH)₂D₃ action in human osteoblast-like cell line TE85.