Decreased protein and puromycinyl-peptide degradation in livers of senescent mice

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Abstract
Liver protein-degradation rates were determined in young and old C57B1 mice by the method of Swick et Ip. Results indicated a marked age-related increase in the half-lives of short-lived proteins in the nuclear, mitochondrial, lysosomal and 100,000 g supernatant cellular fractions, and in total trichloroacetic acid-precipitable proteins. The efficiency of the degradation system in removing aberrant proteins from livers of young and old mice was tested. The time required for 50% disappearance of puromycinyl-peptides changed from .apprx. 20 min in 6-mo.-old mice to .apprx. 150 min in 24-mo.-old animals. In old animals the proteolytic activity involved in degradation of aberrant proteins and, presumably, of native proteins may be markedly defective.