Title: Regulation of glycogen breakdown by glycogen level in contracting rat muscle
Authors: Vandenberghe, K ×
Richter, E A
Hespel, Peter #
Issue Date: Mar-1999
Publisher: Blackwell Publishing
Series Title: Acta Physiologica Scandinavica vol:165 issue:3 pages:307-314
Abstract: The interaction of glycogen concentration, insulin and beta-adrenergic stimulation in the regulation of glycogen breakdown was studied in perfused rat muscles. Rats were pre-conditioned to obtain two groups with either normal (N) or 'supercompensated' (SC) muscle glycogen. The next day their hindlimbs were perfused with a medium containing insulin (0, 40 and 100 microU mL(-1)) and/or isoproterenol (0 and 1.5 nmol L(-1)). Contractions were induced by electrical stimulation of the sciatic nerve. Compared with N, glycogen breakdown in white gastrocnemius during contractions was greater in SC at any hormonal combination (P < 0.05). Conversely, in red gastrocnemius (RG) the higher glycogenolytic rate in SC, compared with N, faded as the insulin concentration was raised from 0 to 100 microU mL(-1). However, isoproterenol restored the higher glycogenolytic rate in SC. In any condition, RG glycogen synthase fractional activity was lower (P < 0.05) during contractions in SC than in N. Furthermore, the percentage of phosphorylase a was higher in SC except when muscles were exposed to insulin alone. In conclusion, high initial glycogen concentration in fast-glycolytic muscle causes high glycogenolytic rate during contractions, irrespective of hormonal stimulation. In contrast, due to down-regulation of phosphorylase activity, such a relationship does not exist in insulin-stimulated fast-oxidative muscle.
ISSN: 0001-6772
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Exercise Physiology Research Group
× corresponding author
# (joint) last author

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