AJP - Endocrinology and Metabolism, Vol 263, Issue 6 E1144-E1150, Copyright © 1992 by American Physiological Society
A reexamination of the effect of exercise on rate of muscle protein degradation
G. J. Kasperek, G. R. Conway, D. S. Krayeski and J. J. Lohne
Department of Biochemistry, East Carolina University School of Medicine, Greenville, North Carolina 27834.
The purpose of this study was to examine the effect of exercise on the rate
of protein degradation in rat skeletal muscle. The rates of total and
myofibrillar protein degradation were determined by the measurement of the
rates of release of tyrosine and 3-methylhistidine, respectively, from the
perfused single rat leg. This method measures the rate of protein
degradation in the entire lower leg and does not suffer from the
limitations inherent in methods that rely on urinary excretion. The rate of
total protein degradation was increased by exercise and involved increased
flux through the lysosomal pathway, while the breakdown of myofibrillar
protein was unchanged. The changes in the rates of protein degradation
during the recovery period were greatly influenced by energy intake. Again
the rate of myofibrillar protein degradation was unchanged or slightly
increased during the recovery period, after either level or downgrade
running. Exercise did prevent the increase in the rate of total protein
degradation caused by food restriction, which may have important
implications in weight reduction diets.
