The Effects of Starvation, Glucose Infusion, and Normal Feeding, on Muscle Protein Synthesis and Catabolism in the Newborn Guinea Pig

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Abstract
We determined the effects of feeding, starvation, and glucose infusion after starvation in newborn guinea pigs. We determined the rate of 14 C-leucine incorporation into skeletal muscle (Ks) as a measure of muscle protein synthesis and the rate of excretion of 3-methylhistidine as a measure of muscle myofibrillar protein catabolism (Kc). Fed newborns, who were in positive nitrogen balance, had the highest Ks and lowest Kc, while starved newborns had the lowest Ks and highest Kc. Infusing glucose after starvation decreased net protein catabolism and Kc, but did not increase Ks. The magnitude of change of Kc in response to starvation and glucose infusion was much greater than Ks. Changes in catabolic rate may influence net muscle protein balance ro a greater degree than changes in synthetic rate.