Effect of Colchicine and Hydrocortisone on Invertase Activity in the Duodenum of the Chick Embryo

Abstract

Invertase activity in the developing chick embryo duodenum was studied in vitro and in vivo in order to clarify the relationship between division and differentiation in this tissue. Duodenal fragments from 16-and 19-day chick embryos were cultured for 2 and 3 days in chemically defined medium without and with hydrocortisone, colchicine, or hydrocortisone and colchicine. For the in vivo experiments, the yolk sacs of 15-day embryos were injected with saline or the above agents. Although hydrocortisone induced invertase activity in the 16-day duodenum in vitro, it caused a decrease in the mitotic count (number of mitoses per 100 villi). Colchicine showed the expected mitotic arrest in cultured tissues but the effect on invertase specific activity was variable. The induction of enzyme activity by hydrocrotisone was increased by colchicine despite the presence of mitotic arrest. These results indicate a direct effect of hydrocortisone in inducing invertase activity within the epithelial cells without the necessity for a divisional event or for alterations in precursor cells. Although experiments in the intact chick embryo were limited by the marked toxicity of colchicine, the effects of hydrocortisone and the combination of hydrocortisone and colchicine in enzyme activity in vivo were similar to those seen in vitro. Additionally, enzyme development in the embryo was found to be exquisitely sensitive to alterations in the environment which may not affect gross or microscopic anatomical structures.