Oxidative phosphorylation of cardiac mitochondria and contraction of glycerol-treated fibers of psoas muscle.

In this paper are reported observations on a system in which adenosine diphosphate and orthophosphate are synthesized into adenosine triphosphate by a respiring mitochondrial suspension supplied with glutamate. The ATP thus synthesized is available to a glycerinated muscle fiber which, upon developing isometric tension, hydrolyzes the ATP back to ADP and P. The hydrolysis products are then available once more to the mitochondria (cf. (1)). The oxygen consumption of the mitochondria is followed polarographically, and the tension of the fiber is recorded by a strain gauge. This compound system can be viewed in various ways. It is, for example, a crude reconstruction of the situation in the living muscle fiber, and its behavior reveals something about the availability of mitochondrial ATP to fibers. On the other hand, it is a new, self-regulating ATP “feeder” system, differing from earlier described feeder systems, such as creatine kinase (2) and pyruvate kinase (3), in that it is truly cyclic.