Using 18-week-old and 52-week-old Wistar rats, we examined interleukin-6 (IL-6) production from osteoblasts and bone marrow macrophages treated with medroxyprogesterone acetate (MPA) and/or β -estradiol. The level of IL-6 production by osteoblasts was increased by treatment with MPA and, reversely, decreased by treatment with β-estradiol. These changes were especially remarkable in osteoblasts of 52-week-old rats. Additionally, and in contrast, the production of IL-6 by bone marrow macrophages was not significantly changed by treatment with both agents. These data suggest that because the increased production of IL-6 by osteoblasts treated with MPA in opposition with β-estradiol, MPA should be careful for osteoporosis dependent upon osteoclasts activated by IL-6. Finally, there was a marked difference in the amount of IL-6 produced between osteoblastd and bone marrow macrophages.
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