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 ov ariectomized OVX rats. Adult OVX rats were treated for 5 wk with vehicle, b oron (5 ppm as boric acid), E-2 (30 mug/kg/d, sc), PTH (60 mug/kg/d, sc), o r a combination of boron and E-2 or PTH, respectively. The E-2 treatment co rrected many adverse effects of OVX on bone quality, increased bone Ca, P, and Mg contents, and decreased trabecular plate separation. Dietary boron s upplementation had no effects on these bone parameters in CVX rats. When OV X rats were treated with boron and E-2 together, trabecular bone volume (Tb .BS/TV) and plate density were increased significantly more than that cause d by E-2 alone. The boron and E-2 combination also increased trabecular bon e 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 b y PTH alone. In summary, this study shows for the first time that boron enh anced the action of E-2, but not that of PTH, to improve trabecular bone qu ality in OVX rats.