Effect of Estrogen on Bone Mineral Turnover in Mature Female Rats as Measured by Strontium-85 1

Abstract

Summary

On a per weight basis, normal mature male and female rats retained the same amount of ⁸⁵Sr at 45-days postinjection, whereas hyperphagic castrate females retained less. However, no difference in ⁸⁵Sr retention was observed between castrate rats on an ad libitum diet and those on a restricted diet. When daily injections of a physiological dose (5μg) of estradiol were administered, retention was (i) significantly greater (12–15%) in estrogen-treated castrate and normal rats on an ad libitum intake compared to untreated rats; (ii) significantly greater (24%) in estrogen-treated castrate rats on a restricted intake compared to untreated castrate rats on an ad libitum intake; and (iii) generally significantly greater in the femurs of estrogen-treated rats compared to untreated rats. Possible mechanisms by which retention was enhanced by the action of estrogen are discussed.