Premium
Glycogen Metabolism in Bovine Adrenal Medulla
Author(s) -
Millaruelo Ana,
Sagarra M. Rosa,
MirasPortugal M. Teresa
Publication year - 1982
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1982.tb08652.x
Subject(s) - glycogen phosphorylase , adrenal medulla , glycogen , glycogen branching enzyme , glycogen synthase , endocrinology , medicine , glycogenesis , biology , glycogen debranching enzyme , biochemistry , chemistry , catecholamine
Glycogen content was determined both in whole adrenal medullary tissue and in isolated adrenal chromaffin cells, in which it responds to glucose deprivation and restoration. [ 14 C]glucose incorporation into glycogen in isolated adrenal chromaffin cells is increased by previous glucose deprivation (“fasting”). Total glycogen synthase activities are 452 ± 66 mU/g in whole tissue and 305 ± 108 mU/g in isolated cells. The K m of glycogen synthase for UDP‐glucose is 0.67 mM with 13 m m glucose‐6‐phosphate and 1 m m without this effector. The in vitro inactivation process of glycogen synthase a has been found to be mainly cyclic AMP‐dependent, but it also responds to Ca 2+ . Total glycogen phosphorylase activities are 8.69 ± 1.26 U/g in whole tissue and 2.38 ± 0.30 U/g in isolated cells. The requirements for interconversion in vitro of both glycogen synthase and phosphorylase suggest a system similar to that of other tissues. During incubation of isolated adrenal chromaffin cells with 5 m m ‐glucose, phosphorylase a activity decreases and synthase a activity increases; these changes are more marked in “fasted” cells. Glycogen content and glycogen synthase and phosphorylase activities are higher in the adrenal medulla than in the brain, suggesting a greater metabolic role of glycogen in the adrenal medulla.