RELATIONSHIP BETWEEN GROWTH AND PROTEIN-TURNOVER RATES AND NUCLEIC-ACIDS IN THE LIVER OF RAINBOW-TROUT (ONCORHYNCHUS-MYKISS) DURING DEVELOPMENT

We have studied the nucleic acid concentrations and protein turnover r ates, fractional protein synthesis (K-S), degradation (K-D), and accum ulation (K-G) rates, synthesis capacity (C-S), synthesis efficiency (K -RNA), synthesis per DNA unit (K-DNA), and protein retention efficienc y (PRE) in the liver of rainbow trout (Oncorhynchus mykiss) at differe nt stages of development (fingerling: 7 g; juvenile: 45, 65, and 170 g ; adult: 420 g; represented by 14-, 24-, 28-, 40-, and 96-week-old fis h). Our results show that liver growth is characterized by linear incr eases in both total DNA (reflecting hyperplasia) and the protein:DNA r atio (reflecting hypertrophy); hyperplasia was more pronounced than hy pertrophy. Development was accompanied by a significant decrease in K- S, while K-G did not change significantly. There was a concomitant fal l in RNA concentration measured as milligrams per gram of protein (C-S ) and as milligrams per gram of liver, while K-RNA only decreased slig htly. The alterations in K-S were thus probably due to a decrease in C -S. The pronounced fall in K-S together with the slight increase in th e protein:DNA ratio may be responsible for the decline in K-DNA. PRE i ncreased concomitantly with an increase in whole-body weight.