SOME FACTORS INFLUENCING PHOSPHATE TURNOVER IN MUSCLE

Abstract

The effects of prolonged stimulation, recovery, and glucose adm. on the uptake of P32 by the P compounds of muscle were studied on cats in the fasting and post-absorptive states. The uptake of P32 by phosphocreatine, the labile phosphate groups of adenosine triphosphate, and fructose-6-phosphate is greater in the post-absorptive state than in fasting. Prolonged contraction is without effect on either the uptake of P32 by any of the acid-soluble organic phosphorus compounds of muscle, or its distribution among them. In recovery from prolonged activity, there is a marked increase in the metabolic turnover rate of all the P compounds present, as evidenced by a higher P32 content. In the post-absorptive state, the adm. of glucose reduces the metabolic turnover rate of phosphocreatine, adenosine triphosphate, and fructose-6-phosphate, but not that of glucose-6-phosphate; these effects are seen both in resting muscle and that recovering from prolonged activity. In the fasting state, the adm. of glucose does not affect the metabolic turnover rate of phosphocreatine and adenosine triphosphate. The findings tend to support the view that an oxidative phosphorylation cycle is involved in the resting metabolism of muscle, but not in the metabolism of muscular contraction, and that glucose-6-phosphate does not take part in this cycle.