Protein Synthesis Studies in Skeletal Muscle of Aging Rats. II. In Vitro Studies With 0.5M Potassium Chloride Washed Polyribosomes

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Abstract
To investigate further the age-related reduction in muscle protein synthesis activity found previously using a crude polyribosome/pH 5 system (Pluskal et al., 1984), a 0.5M KCI washing procedure was utilized to remove the nonribosomal factors from polyribosomes isolated from male Sprague-Dawley rats in the following age groups: young (1 to 2 months), mature (12 months), and aged (22 to 24 months). Using a common source of enriched elongation factor fraction from young animals, it was not possible to demonstrate any significant difference (p> .05) in protein synthesis between the 0.5M KCI-washed polyribosomes isolated from the various age groups. Using a cell-free system containing young salt washed polyribosomes stimulated by the addition of 0.5m KCI-wash fractions, however, it was shown that the mature and aged salt-wash fractions were less (p < .05) active than material from young animals. Thus, the observed decline in protein synthesis efficiency during aging may be attributed to a reduced capacity to promote initiation/ elongation by the nonribosomal salt wash fractions of muscle polyribosomes.