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 thenceforth 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.