Divergent effects of actinomycin d on cortisol and on glucose stimulation of glycogenesis in mouse liver.

1. The administration of cortisol and of other glucocorticoid steroids to starved mice produced an increase in liver glycogen content, an elevation of glycogen-synthetase activity and a predominantly particulate localization of both phosphorylase and glycogen-synthetase enzymes. 2. Three daily doses of actinomycin D caused a marked glycogen depletion, a significant decrease in glycogen-synthetase activity, the solubilization of phosphorylase and glycogen synthetase and the following effects on the activities of various other enzymes: a decrease in UDP-glucose pyrophosphorylase and phosphoglucomutase, an increase in glucose 6-phosphate dehydrogenase and no change in glucose 6-phosphatase, 6-phosphogluconate dehydrogenase, pyruvate kinase and UDP-glucose dehydrogenase. 3. Glucose ingestion, but not cortisol administration, reversed the effects of actinomycin D on liver glycogen content and on the activities of phosphorylase and glycogen synthetase.