Studies of the biochemistry of contracting and relaxing muscle by the use of 31 P n.m.r. in conjunction with other techniques

Abstract

When n.m.r. is applied to suitably chosen biological problems it yields a wealth of fundamental information unmatched by any other technique. By means of $^{31}$P n.m.r. we have studied intact living muscle at rest, during contraction and during recovery from contraction. Phosphocreatine, ATP, inorganic phosphate, phosphorylated intermediaries of glycolysis, pH and the binding of Mg$^{2+}$ to ATP are observed directly in the spectra. From the spectra can be calculated the concentration of free ADP, the free energy change for ATP hydrolysis, the production of lactic acid and the total ATP turnover. Changes in these quantities can thus be followed continuously in vivo and we have shown how they are related to the decline in force development and to the slowing of relaxation that occur during fatigue. Similar methods have been applied to study the control of glycolysis.