Growth, protein-turnover rates and nucleic-acid concentrations in the white muscle of rainbow trout during development.

We have studied the growth rate, nucleic-acid concentration, protein-accumulation rate (K(G)), and several other parameters relating to protein turnover, such as the protein-synthesis (K(S)), and protein-degradation rates (K(D)), protein-synthesis capacity (C(S)), protein-synthesis efficiency (K(RNA)), protein-synthesis rate per DNA unit (K(DNA)) and protein-retention efficiency (PRE), in the white muscle of rainbow trout during development. Both growth rate and relative food intake decreased significantly with age and weight, as did the food-efficiency ratio (FER) and protein-efficiency ratio (PER). Although absolute RNA and DNA contents increased with age, their relative concentrations decreased. The RNA/DNA ratio increased sharply from 14 to 28 weeks but afterwards decreased towards initial values. Hypertrophy increased rapidly to the 28-week stage but henceforth increased much more slowly. Hyperplasia, on the other hand, continued to increase linearly, resulting in a significant four- to fivefold predominance in this type of growth at the end of the 96-week experimental period. K(G) decreased significantly with age, as did K(S), and C(S), whereas at the 14-week stage, K(D) was significantly lower than at other ages. K(RNA) increased until 28 weeks. K(DNA) increased significantly in juvenile fish compared to both fingerlings and adults, where it showed similar lower values. PRE remained high at all ages.