Effects of continuous 17β-estradiol administration on the periosteal and corticoendosteal envelope activity in spayed beagles

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Abstract
Histomorphometric analyses of resorptive and formative parameters of the periosteal and corticoendosteal bone envelopes were performed on ribs from intact, spayed and spayed 17β-estradiol-supplemented Beagle dams. Dynamic formative features were evaluated after 2 pulses ofin vivo tetracycline administration. The results indicated that following oophorectomy there was an increase in resorptive surfaces on the periosteum and corticoendosteum, and a decline in formative activity on these same envelopes. With continuous 17β-estradiol supplementation, the resorptive surfaces on both the periosteum and corticoendosteum of the spayed dams decreased. The formative activity on the periosteum seemed to decline further after the administration of 17β-estradiol, while on the corticoendosteum it tended to be restored to the level obtained for the intact dams. The increase in mineralization lag-time detected on the periosteum following oophorectomy appears not to be corrected by continuous 17β-estradiol supplementation in the spayed dams.