White muscle 20S proteasome activity is negatively correlated to growth rate at low temperature in the spotted wolffish Anarhichas minor

The effect of temperature and mass on specific growth rate ( G ) was examined in spotted wolffish Anarhichas minor of different size classes (ranging from 60 to 1500 g) acclimated at different temperatures (4, 8 and 12° C). The relationship between G and 20S proteasome activity in heart ventricle, liver and white muscle tissue was then assessed in fish acclimated at 4 and 12° C to determine if protein degradation via the proteasome pathway could be imposing a limitation on somatic growth. Cardiac 20S proteasome activity was not affected by acclimation temperature nor fish mass and had no correlation with G . Hepatic 20S proteasome activity was higher at 12° C but did not show any relationship with G. Partial correlation analysis showed that white muscle 20S proteasome activity was negatively correlated to G (partial Pearson's r = −0·609) but only at cold acclimation temperature (4° C). It is suggested that acclimation to cold temperature involves compensation of the mitochondrial oxidative capacity which would in turn lead to increased production of oxidatively damaged proteins that are degraded by the proteasome pathway and ultimately negatively affects G at cold temperature.