Influence of oestrogen and androgen on modelling of the mandibular condylar bone in ovariectomized and orchiectomized growing mice

Oestrogen and androgen exert a substantial influence on bone metabolism but any differences in their influence on modelling of the condyle, a mandibul ar growth sire, have not been fully clarified. The purpose here was to exam ine histological and histochemical differences in the condyle of ovariectom ized (OVX) or orchiectomized (ORX) mice given injections of oestrogen (E-2, 17 beta -oestradiol) or non-aromatizable androgen (DHT, Sa-dihydrotestoste rone). Eight-week-old C57BL/6J mice (n = 170) were used: they were divided equally into six experimental groups (OVX, ORX, OVX + E-2, ORS + E-2, OVX DHT, ORX + DHT), and non-treatment male and female control groups. In each experimental group, five mice were killed 2, 4, 8 and 12 weeks after OVX a nd ORX. Oestrogen or androgen were given daily after the surgery by subcuta neous injection of E-2 or DHT. Increases in the number of tartrate-resistan t acid phosphatase-positive cells induced in the OVX and ORX mice from 4 to 12 weeks after surgery were obviously suppressed by E-2 and DHT. The trabe cular bone volume in the OVX and ORX mice treated with DHT had only increas ed at 12 weeks after surgery, whereas the E-2 injected mice exhibited a sub stantial increase from 4 to 12 weeks after surgery. E-2 injected into the O VX and ORX mice increased the trabecular bone volume earlier than did DHT, and both E-2 and DHT suppressed osteoclast differentiation similarly during the same period. These results suggest that metabolic responses of osteocl asts and osteoblasts to E-2 and DHT may be different, producing somewhat di fferent patterns of bone modelling in males and females. (C) 2000 Elsevier Science Ltd. All rights reserved.