title: An electron microscopic and biochemical study of the effects of glucagon on glycogen autophagy in the liver and heart of newborn rats.
abstract: The effects of glucagon on the ultrastructural appearance and acid glucosidase activities in the liver and heart of newborn rats were studied. Liver or heart glycogen-hydrolyzing activity of acid glucosidase increased 3 hours after birth and gradually decreased from 3 to 9 hours. Maltose-hydrolyzing activity of acid glucosidase also rose 3 hours after birth, maintained a plateau between 3 and 6 hours, and fell at 9 hours. The administration of glucagon increased autophagic activity in the hepatocytes at the age of 6 hours. Glycogen inside the autophagic vacuoles was decreased, apparently due to the increased glycogen degradation. Glycogen-hydrolyzing activity was elevated in both the liver and the heart. Maltose-hydrolyzing activity was elevated in the liver, but not in the heart. The results of this study suggest that the glycogen-hydrolyzing and maltose-hydrolyzing activities of acid glucosidase are due to different enzymes. Glucagon's effect on the glycogen-hydrolyzing acid glucosidase activity and autophagosomal morphology is similar in both the liver and the heart.
authors.affiliation: Department of Anatomy, Histology and Embryology, Medical School, University of Ioannina, 45110 Ioannina, Greece. kondomerkos@hotmail.com
authors.forename: D J
authors.initials: DJ
authors.lastname: Kondomerkos
authors.forename: S A
authors.initials: SA
authors.lastname: Kalamidas
authors.forename: O B
authors.initials: OB
authors.lastname: Kotoulas
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001343:Autophagy / Q000187:drug effects*; D005934:Glucagon / Q000494:pharmacology*; D005959:Glucosidases / Q000378:metabolism; D006003:Glycogen / Q000378:metabolism*; D006321:Heart / Q000187:drug effects / Q000502:physiology; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D008099:Liver / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D008320:Maltose / Q000378:metabolism; D008854:Microscopy, Electron; D009206:Myocardium / Q000378:metabolism* / Q000648:ultrastructure; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology*; D051381:Rats; D013997:Time Factors
chemical_list: D011500:Protein Synthesis Inhibitors; D008320:Maltose; D006003:Glycogen; D005934:Glucagon; D005959:Glucosidases