Control of adaptations in protein levels in response to exercise
1985
Booth, Frank W. | Watson, Peter A.
Extract: The nature of the contractile stimuli to which a skeletal muscle is subjected determines which proteins will increase in skeletal muscle. Rates of muscle protein synthesis decrease during an exercise bout for durations of less than 30 minutes. Synthesis has been reported to increase, remain unchanged, or decrease during exercise bouts lasting from 30 minutes to 7 hours. Protein synthesis rates apparently increase when exercise exceeds 7 hours. After short bouts of exercise, protein synthesis rates in muscles appear to decrease in the first hour after exercise, but in the second hour after exercise increase to levels greater than normal. We hypothesize that decreases in ATP and pH levels in muscle during contractile activity may dampen a calcium-mediated stimulation of translation of RNA. That the content of alpha-actin mRNA in muscles of immobilized limbs is unchanged when actin synthesis initially decreases suggests that a decrease in the translation of actin mRNA is the facilitating step in the decrease in actin synthesis. Rates of muscle protein degradation decrease during exercise if exercise duration is less than 12 hours, but increase when exercise is continuous for a day. After intense exercise, rates of protein degradation in skeletal muscle may be increased. An increased ratio of NAD(P)H:NAD(P) in muscle duing short-term exercise may decrease degradation. Increased lysosomal enzyme activity in muscle occurs during the postexercise period. (Author)
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