The degradation of glycogen in the lysosomes of newborn rat hepatocytes: glycogen-, maltose- and isomaltose- hydrolyzing acid alpha glucosidase activities in liver

S.A. Kalamidas and O.B. Kotoulas

Department of Anatomy, Histology and Embryology, Medical School, University of Ioannina, Ioannina, Greece

Offprint requests to: Dr. Stefanos A. Kalamidas, Department of Anatomy, Histology and Embryology, Medical School, University of Ioannina, Ioannina 45110, Greece

Summary. The lysosomal glucosidase activities and glycogen degradation in newborn rat liver were studied by using biochemical assays, electron microscopy and quantitative morphometry. Glycogen-hydrolyzing, maltose-hydrolyzing and isomaltose-hydrolyzing activities were low at birth but increased afterwards. At the age of 6 hours they were markedly elevated. Actinomycin prevented the development of glucosidase activities indicating that these depend on protein synthesis. Parenteral glucose inhibited all three activities. This was apparently due to the abolition of normal postnatal hypoglycemia and the need for blood glucose. Cyclic AMP increased the glycogen-hydro-lyzing but not the maltose-hydrolyzing activity. Propranolol inhibited the glycogen-hydrolyzing but not the maltose-hydrolyzing activity. The observations of this study provide further support for the hypothesis made by previous investigators that these activities are due to different enzymes. Histol. Histopathol 14, 23-30 (1999)

Key words: Liver, hepatocytes, lysosomes, Glycogen, Alpha-glucosidase


DOI: 10.14670/HH-14.23