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-accumu lation rate (K-G), and several other parameters relating to protein turnove r. such as the protein-synthesis (K-S), and protein-degradation rates (K-D) , protein-synthesis capacity (C-S), protein-synthesis efficiency (K-RNA), p rotein-synthesis rate per DNA unit (K-DNA) and protein-retention efficiency (PRE), in the white muscle of rainbow trout during development. Both growt h 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 2 8 weeks but afterwards decreased towards initial values. Hypertrophy increa sed 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 wit h age, as did K-S, and C-S, whereas at the 14-week stage, K-D was significa ntly lower than at other ages. K-RNA increased until 28 weeks. K-DNA increa sed significantly in juvenile fish compared to both fingerlings and adults, where it showed similar lower values. PRE remained high at all ages. (C) 2 001 Elsevier Science Ltd. All rights reserved.