ANDROGEN-DEPENDENT AND INDEPENDENT PROCESS OF BONE-FORMATION IN THE DISTAL SEGMENT OF OS-PENIS IN THE RAT

The distal segment of the os penis of the rat develops as a fibrocarti lage which is replaced with nonlamellar bone by endochondral ossificat ion after puberty. Development of the fibrocartilage and its calcifica tion have been shown to be induced by androgens, but androgen-dependen cy of the endochondral ossification has not been studied in detail. In the present study, immature male rats of various ages were castrated and the ossification of the fibrocartilage of os penis was examined. I n rats castrated at 6 weeks, when the fibrocartilage was scarcely calc ified, ossification did not occur even at 24 weeks. When the castrated rats were treated with testosterone, ossification started before 12 w eeks of age. In rats castrated at 8 weeks, when the fibrocartilage was heavily calcified, endochondral ossification was observed in some of the animals (5/7) at 24 weeks of age. The results of this study indica te that once the fibrocartilage is calcified, the endochondral ossific ation can take place without androgen, although the androgen can promo te the process of ossification.