Acute Handling Stress Alters Hepatic Glycogen Metabolism in Food-Deprived Rainbow Trout (Oncorhynchus mykiss)

Acute handling stress resulted in significant elevation of plasma cortisol and lactate concentrations within 30 min in both fed and food-deprived rainbow trout (Oncorhynchus mykiss), indicating a typical stress response. Plasma glucose levels rose immediately (30 min) poststress in the food-deprived group, while there was a delayed response (2 h) in the fed group. The low liver glycogen content and total glycogen phosphorylase (GPase) and glycogen synthase (GSase) activities in the food-deprived group indicated an overall depression in glycogen metabolism. Acute handling stress maintained liver glycogen stores for up to 4 h in the food-deprived group, but the combined effects of limited substrate and increased energy demand necessitated mobilization of liver glycogen in the food-deprived group, but not in the fed group. This increased glycogen mobilization in the food-deprived group coincided with a secondary elevation in plasma cortisol concentration 4 h poststress. The results indicated that food-depriv...