Effect of epinephrine administration on glycogen metabolism in red and white muscle of anaesthetized pigs (Sus scrofa domesticus)

Abstract

AbstractThe glycogenolytic effect of exogenous epinephrine was studied in white (Longissimus) and red (Trapezius) muscle of anaesthetized pig. In addition, we assessed the metabolic action of epinephrine during the 3 h following the cessation of perfusion. Twelve purebred Large White pigs, averaging 80 kg live‐weight, were used. The animals were anaesthetized and perfused (0–15 min) with 5 μg kg−1 min−1 epinephrine or saline (control animals). Blood samples were taken to determine plasma levels of glucose, lactate and non‐esterified fatty acids (NEFA). Muscle samples were taken to determine the concentrations of glycogen and related metabolites, and the activity ratio of the enzyme glycogen phosphorylase. 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 treatment induced significant increases in plasma metabolites and an overall significant glycogen depletion. The extent of epinephrine‐induced glycogenolysis was greater in the red Trapezius than in the white Longissimus muscle. This was associated with a greater rise in the muscle lactate content and in the activity ratio of phosphorylase in the Trapezius muscle during epinephrine administration. In both muscles, no significant glycogen depletion was observed during 3 h following the cessation 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.