ALTERATIONS IN THE FRACTIONAL PROTEIN-TURNOVER RATES IN RAINBOW-TROUTLIVER AND WHITE MUSCLE CAUSED BY AN AMINO-ACID-BASED DIET AND CHANGESIN THE FEEDING FREQUENCY

We have studied the effects of an aminoacid-based diet, ABD, (15% free aminoacids plus 30% fish-meal protein) as well as feeding frequency ( two and four times day) on various protein-turnover-rate parameters in the liver and white muscle of rainbow trout (Oncorhynchus mykiss) and have related these parameters with the growth rate and RNA and DNA ce ll contents. Our results showed that in both types of tissue the fract ional rates (Ks) and efficiency, (K(RNA)) of protein synthesis signifi cantly increased when fishes were fed four times compared to those fed only twice. The considerable differences between the fractional rates of protein synthesis (Ks) and protein degradation (K(D)) in white mus cle compared to hepatic tissue explains the high percentage of protein deposition in the former. Thus. about ninety-three percent of the pro tein synthesized in white muscle contributes to growth, while only ele ven percent goes towards growth in the liver.