Effect of Cortisone and Growth Hormones on Cellular Proliferation During Early Embryogenesis.

Abstract

The effects of cortisone and pituitary growth hormone on the embryonal tissues of the chick have been studied at time periods varying between 18 and 72 hours of incubation. No effects were noted at 18 and 30 hours. Mitotic counts have demonstrated the basic mitotic suppressing effect of cortisone in mesoderm at 60 hours and in ectoderm and mesoderm at 72 hours, although there were no changes in endoderm. An increase in mitotic activity was observed in embryos receiving growth hormone in the ectoderm and mesoderm at 60 hours, but not at 72 hours. However, an increase in cell density was observed in these embryonal tissues at 72 hours of incubation. Endoderm was also refractory to growth hormone. Since it is known that development of a functional endocrine system does not occur in the chick embryo before the 7th incubation day, it would appear valid to conclude that these represent direct effects of the hormones rather than the result of indirect mechanisms such as the stimulation of synergistic or suppression of antagonistic hormones.