Observations on the Rate of Incorporation of Phosphorus-32 into Adenosine Triphosphate in Skeletal Muscle

Abstract

Furchgott and Shorr¹ and Kalckar et al.² have pointed out the importance of differentiating between intra- and extra-cellular inorganic phosphorus in the determination of the turnover-rates of adenosine triphosphate and phosphocreatine. This arises particularly in a tissue such as skeletal muscle, where the inorganic phosphorus of the extracellular fluid does not come into rapid equilibrium with that of the intracellular fluid. The perfusion technique of Kalckar et al.² is believed by these authors to eliminate the extracellular phosphorus, but to have no effect on the specific activity of the intracellular adenosine triphosphate and phosphocreatine. The experimental support for this belief² rested on an experiment in which one hind limb of a rabbit was removed after the injection of phosphorus-32 and placed in an ice bath for the time period over which the remaining hind limb was perfused with 1–1.51. of phosphate-free Ringer's fluid. Subsequent analysis of the extracts from the muscles of the two hind limbs revealed identical specific activities in adenosine triphosphate and phosphocreatine. The conclusion that no change occurred in the specific activities in the perfused limb is based on the assumption that no change occurred in the control limb, which was kept in the ice-bath.