Open AccessDirect Activating Effects of Dexamethasone on Glycogen Metabolizing Enzymes in Primary Cultured Rat Hepatocytes
Author(s) -
Baqué Susanna,
Roca Àngela,
Guinovart Joan J.,
Gómezfoix Anna M.
Publication year - 1996
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1996.t01-1-00772.x
Subject(s) - glycogen phosphorylase , glycogen synthase , glycogen , glycogen branching enzyme , glycogenolysis , endocrinology , medicine , dexamethasone , glycogen debranching enzyme , phosphorylase kinase , glycogenesis , hepatocyte , chemistry , enzyme , biochemistry , biology , in vitro
The direct effects of dexamethasone on glycogen synthase and phosphorylase and glycogen content have been investigated in primary cultured rat hepatocytes. Dexamethasone induced the transient translocation of glycogen synthase from the soluble to the 10000 × g pelletable fraction and the activation of this enzyme, although more significant, longer‐standing activation was achieved in the pelletable fraction. Neither total glycogen synthase content nor glycogen synthase mRNA levels were modified. Dexamethasone also caused the sustained activation (up to 6 h) of glycogen phosphorylase, which was not accompanied by an increase in its mRNA level. Glycogen cell content and the incorporation of [ 14 C] glucose into glycogen decreased after dexamethasone treatment. The data show that dexamethasone, unlike other glycogenolytic hormones, at concentrations of 10 nM or higher, stimulate hepatocyte glycogenolysis without inducing the inverse coupling of synthase and phosphorylase. The co‐existence of active forms of both glycogen synthase and phosphorylase promoted by dexamethasone leads to a situation that is analogous to that of the fasted liver.