Effect of cyclosporin A on carbohydrate metabolism of isolated rat liver cells.
Treatment with cyclosporin A may cause hyperglycemia. The mechanisms for this phenomenon are not entirely clear. The effect of cyclosporin A treatment on rat liver phosphoenolpyruvate-carboxykinase and hepatocyte glycogen synthetase and phosphorylase activity was therefore investigated. Glycogen synthetase (total enzyme activity and the active I-form) was elevated in hepatocytes of rats undergoing immunosuppressive treatment with cyclosporin A. Glycogen phosphorylase activity showed no difference compared to hepatocytes from control rats. Activity of phosphoenolpyruvate-carboxykinase in liver homogenates was significantly enhanced after cyclosporin A treatment. Thus, it appears that cyclosporin A treatment stimulates gluconeogenesis, and glucose is used as substrate for glycogen synthesis in vitro. Differences of in vitro and in vivo experiments might be explained by long-term induction of phosphoenolpyruvate-carboxykinase and the short-term effects of cyclosporin A on glycogen synthetase.