Histochemical Study of Bone in Estrogen-treated Rats

¹ Department of Anatomy, School of Medicine, University of Southern California, Los Angeles, California and Western Biological Laboratory, Culver City, California

Subcutaneous injections of estrogenic hormones to male and female rats for 37 weeks produced a decrease in the rate of growth. The diaphysis of the tibia had an "osteosclerotic-like" appearance due to the persistence and fusion of the primary trabeculae. The trabeculae from estrogen-treated animals were characterized by a wide core of calcified cartilage lined by a thin layer of bone. These trabeculae stained a deep red with periodic acid-Schiff and exhibited an abundance of alcian blue-positive material, which also stained very intense violet with toluidine blue. These staining reactions would indicate that there was an alteration in the ground substance of both bone and cartilage. This situation produced an interference in the calcification of the bone, thus inhibiting the resorption of the primary trabeculae and reorganization into their adult structure. Not only was endochondral ossification affected, but intramembranous ossification, as exemplified by the interradicular bone of the molar teeth, also showed similar changes.