Growth, starvation and enzyme activity in white muscle of atlantic cod: at what point do muscle metabolic capacities change?

Abstract

Muscle protein decreases only during prolonged starvation of Atlantic cod (Gadus morhua, Gadidae), but in the absence of protein renewal, muscle metabolic capacities may decrease before marked loss of muscle protein. This study aimed at elucidating the threshold at which decreases in growth and condition reduce muscle metabolic capacities, as well as identifying the indicators that best explain changes in metabolic capacities. To generate a wide spectrum of individual growth rates, condition factors and proximate compositions, cod showing different initial condition were fed or starved for different periods of time. The relationships between muscle proteins and metabolic enzyme activities (LDH and CCO) on one hand, and growth rate, condition factor, hepato- and gonadosomatic index and muscle and liver water and energy contents, on the other hand, were examined through linear regression models. Multiple linear regressions explained a large proportion of the observed variability in proteins and enzyme activities. Changes in LDH and CCO activities were not driven by changes in growth rate. Muscle water was the only significant correlate for both enzymes. Enzyme activities decreased as soon as muscle water began to rise. Increases in water content from 79 to 92% resulted in a 10-fold decrease in LDH and CCO activities.

Keywords:

• Condition factor
• Cytochrome c oxidase
• Enzymes
• Gadus morhua
• Growth rate
• Lactate dehydrogenase
• White muscle

Acknowledgements

The authors thank Steve Chouinard, Yves Gagnon and Mario Péloquin for monitoring the experiment and for tissue analysis. Captain Mario Bernard and the crew onboard RV Calanus II helped us with fish capture.