EFFECT OF EPINEPHRINE ADMINISTRATION ON GLYCOGEN-METABOLISM IN RED AND WHITE MUSCLE OF ANESTHETIZED PIGS (SUS SCROFA DOMESTICUS)

The glycogenolytic effect of exogenous epinephrine was studied in whit e (Longissimus) and red (Trapezius) muscle of anaesthetized pig. In ad dition, we assessed the metabolic action of epinephrine during the 3 h following the cessation of perfusion. Twelve purebred Large White pig s, averaging 80 kg liveweight, were used. The animals were anaesthetiz ed and perfused (0-15 min) with 5 mu g kg(-1) min(-1) epinephrine or s aline (control animals). Blood samples were taken to determine plasma levels of glucose, lactate and non-esterified fatty acids (NEFA). Musc le samples were taken to determine the concentrations of glycogen and related metabolites, and the activity ratio of the enzyme glycogen pho sphorylase. Control animals showed stable levels of plasma and muscle metabolites during the 3 h anaesthesia. However, the resting level of the activity ratio of phosphorylase was high (80%). Epinephrine treatm ent induced significant increases in plasma metabolites and an overall significant glycogen depletion. The extent of epinephrine-induced gly cogenolysis was greater in the red Trapezius than in the white Longiss imus muscle. This was associated with a greater rise in the muscle lac tate content and in the activity ratio of phosphorylase in the Trapezi us muscle during epinephrine administration. In both muscles, no signi ficant glycogen depletion was observed during 3 h following the cessat ion of epinephrine administration. This occurred despite the fact that the activity ratio of phosphorylase remained high in the Longissimus muscle until the end of the experiment.