Effect of physiological ADP concentrations on contraction of single skinned fibers from rabbit fast and slow muscles

Assay and chromatographic studies indicate that the direct inhibition of actomysin during muscle fatigue does not involve adenosine diphosphate (ADP), as confirmed by a measurement of physiological concentrations of MgADP on single skinned fibers' unloaded shortening velocity and isometric force during fatigue of rabbit fast- and slow-twitch muscles. Changes in creatine concentration using buffer solutions help vary the MgADP levels in the presence of phosphocreatine and creatine kinase and enable ADP and ATP temporal and spatial buffering.