DIFFERENTIAL RESPONSES OF MANDIBULAR CONDYLE AND FEMUR TO ESTROGEN DEFICIENCY IN YOUNG-RATS

This response of condyle and femur was evaluated by histomorphometry. Five female Sprague-Dawley rats, 6 weeks of age, were subjected to bil ateral ovariectomy, and five others were sham-operated. They were then killed 32 days later. Ovariectomy significantly increased the total t hickness of the condylar cartilage and distal femoral growth-plate car tilage in the young, growing rats. Ovariectomy caused a 2-fold increas e in thickness of the proliferative layer and a 4-fold increase in thi ckness of the hypertrophic layer in the condylar cartilage, and a 1.3- fold increase in thickness of the proliferative layer in the epiphysea l growth cartilage of the femur. Ovariectomy had no effect on the perc entage of trabecular bone volume, the percentage of the bone surface c overed by osteoblasts (Ob.S/BS) and osteoclasts (Oc.S/BS), and number of osteoclasts per bone surface (N.Oc/BS) in the mandibular condyle. O n the contrary, ovariectomy caused a 68.5% decrease in bone volume, a 4-fold increase in Ob.S/BS, and 2-fold increases in Oc.S/BS and N.Oc/B S in the secondary spongiosa of the rat distal femur. Thus there was a prominent difference in the response to oestrogen deficiency between the mandibular condyle and femur in young growing rats. (C) 1998 Elsev ier Science Ltd. All rights reserved.