DEVELOPMENT OF METABOLIC ENZYME-ACTIVITY IN LOCOMOTOR AND CARDIAC MUSCLES OF THE MIGRATORY BARNACLE GOOSE

Preflight development of the goslings was typified by rapid increases in the mitochondrial enzymes of the semimembranosus and heart ventricu lar muscles resulting in near-adult values by 3 wk of age. In contrast , aerobic capacity of the pectoralis muscle initially developed slowly but showed a rapid increase between 5 and 7 wk of age, in preparation for becoming airborne. Activities of glycolytic enzymes in the pector alis muscle showed similar patterns of development as those found for the aerobic enzymes, except for hexokinase, which was low at all ages, indicating an adaptation for catabolism of both intracellular glycoge n and plasma fatty acids in preference to plasma glucose. Muscle mass specific activity of citrate synthase in the pectoralis increased by o nly 33% from goslings during the first few days of flight, compared wi th premigratory geese. Activities of anaerobic glycolytic enzymes in t he ventricles were low, but values for hexokinase, which is involved i n the phosphorylation of plasma glucose, developed rapidly. Values for lactate dehydrogenase were also high, reflecting the capacity of the heart to catabolize plasma lactate. Substrate flux supplied by carniti ne palmitoyltransferase and oxoglutarate dehydrogenase (OGD), in the p ectoralis muscles of the premigratory geese, appears to have the small est excess capacities to meet the requirements of sustained aerobic fl ight. The average maximum oxygen uptake for premigratory geese during flight, as indicated by values for OGD, is calculated to be 484 ml O-2 /min (or 208 ml O-2 . min(-1). kg(-1)).