Effect of 17 beta-estradiol or alendronate on the bone densitometry, bone histomorphometry and bone metabolism of ovariectomized rats

The objective of the present study was to evaluate the effect of 17 beta -e stradiol or alendronate in preventing bone loss in 3-month-old ovariectomiz ed Wistar rats, One group underwent sham ovariectomy (control, N = 10), and the remaining three underwent double ovariectomy. One ovariectomized group did not receive any treatment (OVX, N = 12). A second received subcutaneou s 17 beta -estradiol at a dose of 30 mug/kg for 6 weeks (OVX-E, N = 11) and a third, subcutaneous alendronate at a dose of 0.1 mg/kg for 6 weeks (OVX- A. N = 8). Histomorphometry, densitometry, osteocalcin and deoxypyridinolin e measurements were applied to all groups. After 6 weeks there was a signif icant decrease in bone mineral density (BMD) at the trabecular site (distal femur) in OVX rats. Both alendronate and 17 beta -estradiol increased the BMD of ovariectomized rats, with the BMD of the OVX-A group being higher th an that of the OVX-E group. Histomorphometry of the distal femur showed a d ecrease in trabecular volume in the untreated group (OVX), and an increase in the two treated groups, principally in the alendronate group. In OVX-A t here was a greater increase in trabecular number. An increase in trabecular thickness, however, was seen only in the OVX-E group. There was also a dec rease in bone turnover in both OVX-E and OVX-A. The osteocalcin and deoxypy ridinoline levels were decreased in both treated groups, mainly in OVX-A. A lthough both drugs were effective in inhibiting bone loss. alendronate prov ed to be more effective than estradiol at the doses used in increasing bone mass.