Relationship between growth and protein turnover rates and nucleic acids in the liver of rainbow trout (Oncorhynchus mykiss) during development

Abstract

We have studied the nucleic acid concentrations and protein turnover rates, fractional protein synthesis (KS), degradation (KD), and accumulation (KG) rates, synthesis capacity (CS), synthesis efficiency (KRNA), synthesis per DNA unit (KDNA), and protein retention efficiency (PRE) in the liver of rainbow trout (Oncorhynchus mykiss) at different 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 fish). Our results show that liver growth is characterized by linear increases in both total DNA (reflecting hyperplasia) and the protein:DNA ratio (reflecting hypertrophy); hyperplasia was more pronounced than hypertrophy. Development was accompanied by a significant decrease in KS, while KGdid not change significantly. There was a concomitant fall in RNA concentration measured as milligrams per gram of protein (CS) and as milligrams per gram of liver, while KRNAonly decreased slightly. The alterations in KSwere thus probably due to a decrease in CS. The pronounced fall in KStogether with the slight increase in the protein:DNA ratio may be responsible for the decline in KDNA. PRE increased concomitantly with an increase in whole-body weight.