Is the growth rate of fish set by digestive enzymes or metabolic capacity of the tissues? Insight from transgenic coho salmon

The aim of this study was to compare metabolic and digestive enzyme activities in fish with different growth capacities using growth hormone transgenic and nontransgenic coho salmon (Oncorhynchus kisutch) as a model system. The following enzyme activities were measured: trypsin and chymotrypsin in pyloric caeca, alkaline phosphatase in intestine, pyruvate kinase (PK), lactate dehydrogenase (LDH) and citrate synthase (CS) in gills and white muscle. Transgenic salmon showed higher LDH activity in muscle and PK activities in muscle and gills, whereas chymotrypsin activity in pyloric caeca was higher in the control group. No significant differences were observed between transgenic and control groups for CS, trypsin and alkaline phosphatase activities. The small or no differences observed in this study suggests that the enzyme activities measured were not related to the high growth rate of the transgenic coho salmon. (C) 2002 Published by Elsevier Science B.V.