Skeletal Muscle Protein Synthesis and Degradation Rates of 1, 2, and 4 Week Old Boars and Castrates Measured in Vitro
Skjaerlund, David M.
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The elevated plasma concentrations of testosterone observed in pigs for the first few weeks postnatally was used as the basis for the study of the effects of endogenous testosterone on body growth, muscle growth, and skeletal muscle protein degradation and protein synthesis rates as measured in vitro. Twelve male pigs were castrated at birth for ablation of testosterone and compared to 12 boars at 1, 2, and 4 weeks of age. Protein synthesis rates were measured by the incorporation of L-[2,3,5,6-3H] tyrosine into isolated skeletal muscle protein and degradation rates were measured by monitoring the release of tyrosine in the presence of cycloheximide. No differences in the body weight and individual muscle weights were observed between boars and castrates in all age groups. Boars had lower degradation rates than castrates at 1 week, the same rates at 2 weeks, and higher rates at 4 weeks of age. Protein synthesis rates did not differ between boars and castrates but were highest at 1 week and declined with age.