DIETARY-PROTEIN EFFECTS ON GROWTH AND FRACTIONAL PROTEIN-SYNTHESIS AND DEGRADATION RATES IN LIVER AND WHITE MUSCLE OF RAINBOW-TROUT (ONCORHYNCHUS-MYKISS)

We have studied the effects of a decrease in dietary protein on the gr owth and Protein-turnover parameters [fractional protein synthesis (K( S)), degradation (K(D)) and accumulation (K(G)) rates, synthesis capac ity (C(S)), synthesis efficiency (K(RNA) and K(DNA)). and protein rete ntion efficiency (PRE)]. The administration of a low-protein diet caus ed a significant decrease in the availability of protein precursors du e to a decline in feed efficiency and thus a concomitant decrease in w hole-body, white-muscle and liver growth capacity throughout the exper imental period. The reduction in dietary protein caused a significant decrease in the K(G) value in the liver as a consequence of a decrease in protein retention efficiency (PRE). In white muscle, however, a co nsiderable reduction in the K(G) value was due to a decrease in K(S), C(S), K(DNA) and K(RNA) rather than a decrease in PRE.