Abstract
In order to study the effects of thyroid hormone on liver glycogen, muscle glycogen and liver lipid, male chicks (White-Leghorn, Shaver strain) were surgically thyroidectomized at 11-12 days of age and injected with 1.5μg/10g body weight of L-thyroxine (T4) at 27 days.
In the first trial, thyroidectomized chicks showed a remarkable increase in liver glycogen and liver lipid, and a decrease in muscle glycogen, compared to the control chicks. Thyroxine injection into the thyroidectomized chicks brought the marked decrease of liver glycogen accumulated and an increase in muscle glycogen at 24 hours after injection. However, contents of liver lipid remained unchanged by T4 injection, suggesting that the response of liver glycogen to the injection was more rapid than that of liver lipid.
In the second trial, thyroidectomized chicks were made to fast for 24 hours after the T4 injection. Liver glycogen decreased with time in both thyroidectomized and T4 injected chicks and thyroidectomized chicks. The rate of decrease was more rapid in thyroidectomized and T4 injected chicks than that in thyroidectomized chicks and the difference in liver glycogen contents were significant at 16 and 24 hours after injection. In thyroidectomized and T4 injected chicks, muscle glycogen increased after the first 4-hour depletion, although in thyroidectomized chicks it decreased at a small rate and the difference in muscle glycogen contents were significant at 16 and 24 hours after the injection. The time course of increase in muscle glycogen appeared to be synchronized with that of a decrease in liver glycogen, suggesting that the thyroid hormone plays a role in the regulation of glycogen contents between the liver and muscle.
