Dietary boron supplementation enhanced the action of estrogen, but not that of parathyroid hormone, to improve trabecular bone quality in ovariectomized rats

This study investigated whether boron would enhance the ability of 17 beta -estradiol (E-2) or parathyroid hormone (PTH) to improve bone quality in ovariectomized OVX rats. Adult OVX rats were treated for 5 wk with vehicle, boron (5 ppm as boric acid), E-2 (30 mug/kg/d, sc), PTH (60 mug/kg/d, sc), or a combination of boron and E-2 or PTH, respectively. The E-2 treatment corrected many adverse effects of OVX on bone quality, increased bone Ca, P, and Mg contents, and decreased trabecular plate separation. Dietary boron supplementation had no effects on these bone parameters in CVX rats. When OVX rats were treated with boron and E-2 together, trabecular bone volume (Tb.BS/TV) and plate density were increased significantly more than that caused by E-2 alone. The boron and E-2 combination also increased trabecular bone surface (Tb.BV/TV) and decreased trabecular plate separation in OVX rats. In contrast, whereas daily PTH injection also increased bone Ca, Mg, and P contents, Tb.BV/TV, Tb.BS/TV, trabecular plate density and thickness, and decreased trabecular plate separation in OVX rats, the combination of boron and PTH had no additional improvement in bone quality over that achieved by PTH alone. In summary, this study shows for the first time that boron enhanced the action of E-2, but not that of PTH, to improve trabecular bone quality in OVX rats.