Electron microscopic and biochemical study of the effects of rapamycin on glycogen autophagy in the newborn rat liver.

The effects of rapamycin on glycogen autophagy in the newborn rat liver were studied using biochemical determinations, electron microscopy, and morphometric analysis. Rapamycin increased the fractional volume of hepatocytic autophagic vacuoles, the liver lysosomal glycogen-hydrolyzing activity of acid glucosidase, the degradation of glycogen inside the autophagic vacuoles, and decreased the activity of acid mannose 6-phosphatase. These findings suggest that rapamycin, a known inhibitor of the mammalian target of rapamycin (mTOR) signaling, induces glycogen autophagy in the newborn rat hepatocytes. mTOR may participate in the regulation of this process. Copyright 2004 Wiley-Liss, Inc.