Changes of Bone Mineral Density and IL-6 Levels after Bilateral Ovariectomies in Rats

Han, Seung Yeup; Kim, Sung Han; Park, Keun Yong

Abstract

OBJECTIVE
Estrogen is a major regulator/modulator of bone metabolism, and bone loss in estrogen deficiency is associated with increased bone turnover, But the mechanism for estrogen action on bone metabolism is still unknown. Recent studies have suggested that the increase in bone loss induced by estrogen deficiency is mediated by increased paracrine production of bone resorbing cytokines. Among cytokines, 1nterleukin-6(IL-6) is released from osteoblasts in estrogen deficiency and increases bone resorption by stimulation of osteoclastic activities and recruitment. Thus we performed this study to evaluate the effect of ovariectomies on bone mineral density and IL-6 in cultured monocytes of peripheral blood and bone marrow.
METHODS
The experimental animals were 13 female Sprague-Dawley rats that were 8 weeks of age and weighed an average of 188.5 gram at the beginning of the study. Bilateral ovariectomies were performed in all rats from a ventral approach. Bone mineral density(BMD) of the total body, spine and level of IL-6 of cultured monocytes of peripheral blood and bone marrow were measured before and 8 weeks after ovariectomy.
RESULTS
1) BMD of total body and spine were lower after ovariectomy(0.257+/-0.069g/cm2, 0,208+/-0.005g/cm2) than before ovariectomy (0.276+/-0.005g/cm2, 0.229+/-0.011g/cm2), respectively (P<0.01). 2) Although IL-6 level of cultured monocytes in peripheral blood tended to be higher after ovariectomy than before ovariectomy, this difference was not statistically significant (P>0.05). 3) IL-6 level of cultured monocytes in bone marrow was higher after ovariectomy(82.78+/-4.99pg/ml) than before ovariectomy(48.85+/-2.42pg/ml)(P<0.05).
CONCLUSION
It is possible that increased production of IL-6 in estrogen deficiency induced by ovariectomy occurs in the local environment of bone or bone marrow rather than in the pheripheral blood and stimulates bone resorption.