Tissue protein turnover is altered during catch-up growth following Escherichia coli infection in weanling rats.
Infection in young growing animals is manifested by poor tissue protein accretion; during subsequent catch-up growth this is reversed. To account for these changes, protein synthesis and degradation were measured in vivo in skeletal muscle, skin, liver and small intestine in weanling rats during catch-up growth after Escherichia coli infection. Observations were made at d 4, 6, 8, 11 and 14, when infected rats had elevated nitrogen balance. Liver protein mass and turnover were not affected by treatment. Although protein mass of small intestine fell during infection, catch-up was achieved before d 4, suggesting a high priority for protein repletion in this tissue. On d 4, protein mass was lower (P < 0.05) in muscle (-19%) and skin (-23%) in infected vs. control rats. Thereafter growth rates of skeletal muscle and skin were higher (P < 0.001) in infected rats compared with controls. Catch-up growth was most pronounced early, but continued throughout the study. During catch-up growth, protein synthesis (mg/d) in muscle and skin was not different between control and infected animals. Protein synthesis was maintained in muscle because RNA mass was maintained. During catch-up growth in muscle and skin of infected rats, there was lower protein degradation (mg/d) than in controls (P < 0.05). We conclude that alterations in protein turnover during catch-up growth are tissue and time dependent and are different from those described in other hyperanabolic states.
Samuels
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SE
Department of Animal Science, University of Alberta, Edmonton, Canada.
Baracos
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VE
D000818:Animals; D001835:Body Weight; D004435:Eating; D004927:Escherichia coli Infections / Q000503:physiopathology*; D005260:Female; D006128:Growth; D007421:Intestine, Small / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D010649:Phenylalanine / Q000378:metabolism; D014176:Protein Biosynthesis; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012867:Skin / Q000378:metabolism; D014886:Weaning
D011506:Proteins; D010649:Phenylalanine; D009584:Nitrogen