Selective changes in the protein-turnover rates and nature of growth induced in trout liver by long-term starvation followed by re-feeding.
We report upon the effects of a cycle of long-term starvation followed by re-feeding on the liver-protein turnover rates and nature of protein growth in the rainbow trout (Oncorhynchus mykiss). We determined the protein-turnover rate and its relationship with the nucleic-acid concentrations in the livers of juvenile trout starved for 70 days and then re-fed for 9 days. During starvation the total hepatic-protein and RNA contents decreased significantly and the absolute protein-synthesis rate (A(S)) also fell, whilst the fractional protein-synthesis rate (K(S)) remained unchanged and the fractional protein-degradation rate (K(D)) increased significantly. Total DNA content, an indicator of hyperplasia, and the protein:DNA ratio, an indicator of hypertrophy, both fell considerably. After re-feeding for 9 days the protein-accumulation rates (K(G), A(G)) rose sharply, as did K(S), A(S), K(D)), protein-synthesis efficiency (K(RNA)) and the protein-synthesis rate/DNA unit (K(DNA)). The total hepatic protein and RNA contents increased but still remained below the control values. The protein:DNA and RNA:DNA ratios increased significantly compared to starved fish. These changes demonstrate the high response capacity of the protein-turnover rates in trout liver upon re-feeding after long-term starvation. Upon re-feeding hypertrophic growth increased considerably whilst hyperplasia remained at starvation levels.
Peragón
J
J
Department of Biochemistry and Molecular Biology, Centre of Biological Sciences, University of Granada, Spain.
Barroso
J B
JB
García-Salguero
L
L
Aranda
F
F
de la Higuera
M
M
Lupiáñez
J A
JA
D000222:Adaptation, Physiological; D000818:Animals; D002455:Cell Division; D004247:DNA / Q000032:analysis / Q000096:biosynthesis; D004435:Eating; D006529:Hepatomegaly / Q000378:metabolism; D006965:Hyperplasia / Q000378:metabolism; D008099:Liver / Q000166:cytology / Q000378:metabolism* / Q000473:pathology*; D017686:Oncorhynchus mykiss / Q000502:physiology*; D011506:Proteins / Q000378:metabolism*; D012313:RNA / Q000032:analysis / Q000096:biosynthesis; D012016:Reference Values; D013217:Starvation / Q000378:metabolism*; D013997:Time Factors
D011506:Proteins; D012313:RNA; D004247:DNA