Immobilization of rat hindlimbs at less than resting length caused exponential decay in muscle weight and proteins with a half-time of 4-6 days, whereas stretching delayed atrophy.
The hindlimbs of rats were immobilized, in plaster casts, for varying durations, and the time course for atrophy of muscle and of selected proteins in these muscles was determined. In those muscles whose lengths were at less than resting length during the fixation procedures, exponential decay to a new apparent steady state after atrophy was shown by wet and dry muscle weights and by the amounts of biuret protein, cytochrome c, and citrate synthase. The time taken to decrease to one-half of the final decrease at the new apparent steady state level was about 4-6 days for the above parameters which decayed exponentially. In contrast, the myoglobin concentration increased during atrophy and the amount of myoglobin remain unchanged during atrophy. When fixation procedures on limbs were such that muscles were stretched to lengths greater than resting length, then the onset of atrophy was delayed; indeed, in some cases muscles hypertrophied when fixed in the stretched position.
Frank W. Booth (Sat,) conducted a other in Muscular atrophy. Immobilization of hindlimbs in plaster casts was evaluated on Time course for atrophy of muscle and selected proteins. Immobilization of rat hindlimbs at less than resting length caused exponential decay in muscle weight and proteins with a half-time of 4-6 days, whereas stretching delayed atrophy.