Biochemical changes in tissues of goldfish acclimated to high and low temperatures—I. protein synthesis

Abstract

1. 1. The initial rate of protein synthesis, as measured by the level of incorporation in 1 hr of 14C-leucine into protein, exhibited a compensation in gill and liver of goldfish acclimated at 5°C only when tested at 25°C. However, muscle of 5°C fish showed a greater incorporation than that of 25°C fish at 15°C and 25°C but not at 5°C. The Q 10 of the incorporation rate was higher for the 25°C-acclimated fish than for the 5°C-acclimated ones in the lower range of temperature, but this relationship was reversed in the higher thermal range. 2. 2. All the tissues reached a steady-state level of incorporation within 6–12 hr after the injection of the isotopic precursor in both the cold- and warm-adapted fish, when measured at 15°C. 3. 3. The maximal net synthesis of protein at 12 hr of incorporation was 100–500 per cent higher in the cold-acclimated tissues than in the warm-acclimated ones at 5°C and less so at 15°C. There were no significant differences between the cold- and warm-adapted gill and liver in the net protein synthesis at 25°C, although muscle showed a 50 per cent reduction in this process during warm acclimation. 4. 4. The 14C-count in the PCA-supernatants of the warm-acclimated tissues was higher than in the cold-acclimated, ones, when measured 1 hr after the injection of 14C-leucine at 15°C; this might signify a greater amino acid permeability of the cell membrane during warm acclimation. However, no difference was found in 14C-counts of the PCA-soluble pools of the corresponding tissues from cold- and warm-adapted fish, when measured either at 5° or 25°C, 12 hr after the administration of the isotope. Thus the availability of the precursor did not seem to be rate limiting for the protein synthesis, although a rapid metabolism of the amino acids in the warm-adapted fish tissues cannot be excluded. 5. 5. It is concluded that the translational increase in enzymatic activities and oxidative metabolism of goldfish during cold acclimation may be achieved by a complicated rotational (gill and liver) or a simple translational (muscle) augmentation of the maximal net synthesis of proteins.