Effect of cyclosporin A on carbohydrate metabolism in the rat.

Liver and kidney carbohydrate metabolism was investigated in rats treated with daily doses of 15 mg/kg body weight cyclosporin A (CyA) for 2 and 8 weeks or of 50 mg/kg body weight CyA for 2 weeks. The higher dosage caused significantly reduced liver glycogen and liver glycogen synthetase activity (of both active I-form and total enzyme activity), whereas the activity of the glycogen-degrading enzyme phosphorylase (active a-form and total activity) remained unchanged. Plasma glucose and glucagon levels, as well as blood ketone bodies of these animals, increased significantly and plasma insulin decreased. In contrast, kidney glycogen and glucose content were higher in rats treated with 50 mg CyA, probably due to enhanced ketone body utilization. Reduced liver glycogen synthetase activity was also found in rats treated with 15 mg CyA. Our data suggest that hypoinsulinemia, induced by CyA, might be a contributing factor to the hyperglycemia, which is mainly due to inhibition of liver glycogen synthesis.