METABOLIC ORGANIZATION OF LIVER AND SOMATIC MUSCLE OF LANDLOCKED SEA LAMPREY, PETROMYZON-MARINUS, DURING THE SPAWNING MIGRATION

The metabolic organization of liver acid muscle of the landlocked sea lamprey, Petromyzon marinus, during the spring spawning migration was assessed by measuring activities of key enzymes for several metabolic pathways, the oxidative properties of mitochondria, and plasma concent rations of nonesterified fatty acids (NEFAs) and free amino acids. The se determinations indicate that several metabolic sources are used to fuel the energy requirements of muscle. Lamprey muscle has a high capa city to oxidize lipids but the plasma NEFAs are lower than those repor ted for other species. Of the NEFAs measured in plasma, 18:0 was promi nent, accounting for 23% of the total NEFA content of the plasma. High plasma concentrations of ketogenic amino acids and high levels of tis sue ketogenic/ketolytic enzyme activities indicate that ketone bodies may also be a major fuel source for migrating sea lampreys. Based on m itochondrial oxidation and enzyme measurements, glutamine catabolism i n somatic muscle of lampreys is less important than in other fish red muscle.