Starvation and the activities of glycolytic and gluconeogenic enzymes in skeletal muscles and liver of the plaice,Pleuronectes platessa

Abstract

Changes in body index parameters and liver, red muscle and white muscle enzyme profiles have been determined in fed and four month starved plaice,Pleuronectes platessa. The results are compared to other vertebrates to estimate specific tissue metabolic patterns and changes in these patterns with starvation. 1. Liver demonstrates the lowest glycolytic but highest gluconeogenic capacity of the three tissues. Red muscle has little, if any, gluconeogenic potential, based upon low activities of phosphoenol pyruvate carboxykinase and glucose-6-phosphatase and no detectable activities of pyruvate carboxylase. Plaice white skeletal muscle has the highest glycolytic potential of the tissues studied. 2. Plaice starved for four months demonstrate significant reductions in liver-somatic index and red muscle-somatic index, and increases in tissue water contents (Table 1). Enzyme activities generally decline in both muscle types, but are maintained in the liver (Table 2). Activities of liver soluble phosphoenol pyruvate carboxykinase increase by approximately 8-fold, suggesting that the enzymic response to starvation in plaice is similar to that of mammals. 3. These results suggest that starvation in plaice is associated with both a decrease in spontaneous activity and metabolic capacity of skeletal muscles, and an enhanced potential for liver gluconeogenesis. Also, it is possible that the precursors for liver gluconeogenesis do not form pyruvate as an intermediate step.