Abstract
Under natural lighting condition Donryu rats were bred to see whether a daily cycle of naturally occurring level in liver tyrosine aminotransferase activity would be operated. There seemed to be at least two kinds of mechanism in the regulation of the enzyme, i. e., the one increase of the activity at dust, related to an adrenal function, and the other induction at night, regulated by a protein content in the diet.
Next, a different induction process in the liver enzyme after hormone treatments in vivo was observed. In the experiments using either hydrocortisone or glucagon more significant modification in the enzyme activity was observed in the male rats aged of five weeks old, compared to that in the other groups of rats, especially, in the corresponding female rats or in the rats aged of three weeks old. After an insulin treatment different pattern of the enzyme regulation was observed between the rats aged of three and five weeks old. Usefulness of the controlled feeding condition on the study of enzyme regulation in rat liver was discussed briefly.
