Effects of Extract of Cattle Anterior Pituitary Gland on Endochondral Ossification in Young Guinea Pigs

It has been established that the anterior pituitary gland enhances bodily growth as a whole, but it is not yet known whether it has a specific effect on the growth of cartilage and bone and, if this should be so, wherein the effect consists. We wished, therefore, to study the action of anterior pituitary gland extract on the epiphyseal cartilage and bone formation in young not yet fully grown guinea pigs.

About 30 guinea pigs (fall and winter animals) on the average weighing 130 to 220 gm. were injected with from 1 to 1 1/2 cc. extract 1 daily. Additional guinea pigs, of similar weight, were not injected and served as controls. The injections were continued up to 21 days. After 4, 6, 11, 14, and 21 days, the animals were killed and tibia and fibula were used for the study of the epiphyseal line. In each case the specimen, as a whole, was fixed in 10% formalin; then put into absolute alcohol and subsequently transferred into ether for 2 days, in order to remove the fat from the bone-marrow. The bones were then washed in running water and decalcified incompletely in order to preserve and demonstate the calcium salts. In accordance with Pommer's method, they were kept about 3 to 8 weeks in Mueller's solution, until they had become sufficiently soft for cutting; subsequently they were embedded in celloidin and stained with hematoxylin-eosin or hematoxylin-Van Gieson.

After 4 injections, a stimulation of the growth of cartilage and bone can be seen at the epiphyseal line. The undifferentiated mesenchymal cells have become mobilized and transformed into chondrocytes and osteocytes. The columnar resting cartilage cells are increased in size and number, mitotic figures are found everywhere and are more numerous than under normal conditions, the stroma between the cells correspondingly is much diminished in amount. Likewise in the layer of the vesicular cartilage, hyperplasia and hypertrophy are noted. After 7 to 10 injections, the epiphysis as a whole, has become more narrow in comparison with that of the control animals.