EFFECT OF CRYSTALLINE ESTRIN IMPLANTS ON THE PROXIMAL TIBIA AND COSTOCHONDRAL JUNCTION OF YOUNG FEMALE RATS

Abstract

High levels of estrin, in 1 wk., caused an involution of the proximal growth cartilage of the tibia of young adult [female] rate. After 3 weeks'' treatment the epiphyseal cartilage partially recovered growth capacity and a striking mass of thick trabeculae filled the upper 5th of the diaphyseal marrow cavity. After 6 wks. of estrinization, some signs of resorption and reorganization into thicker more widely spaced trabeculae were noticeable at the distal end of the mass of trabeculae. Increased periosteal or endosteal activity was not observed in any estrinized rat. After estrinization, the growth disc of the costochondral junction displayed a series of regressive changes that increased in severity with the prolongation of treatment. The initial regressive change followed by a recovery in growth activity as seen in the epiphyseal disc of the tibia was not as marked in the costochondral junction. Excessive formation of bony trabeculae was not apparent in the costochondral junction although thicker and longer trabeculae were found beneath the growth disc of treated rats than were found in the controls. Irregular bony plates in juxtaposition to the growth disc that seal off the cartilage cell columns were seen in the costochondral junction and not in the epiphyseal cartilage of the tibia after 6 weekly implants of estrin pellets. The principal distinguishing characteristic of the reaction in the tibia and rib was the difference in amt. and distribution of osseous tissue after estrogen treatment.