MITOCHONDRIAL OXIDATIVE-PHOSPHORYLATION IN SAPONIN-SKINNED HUMAN MUSCLE-FIBERS IN STIMULATED BY CAFFEINE

The addition of 15 mM caffeine to saponin-skinned human muscle fibers from M. vastus lateralis caused in the presence of 2 mM ATP an approx. 2-fold stimulation of respiration with glutamate + malate. This effec t can be abolished by either the addition of the Ca2+ chelator EGTA, t he inhibitor of Ca2+ transport Ruthenium red and the inhibitor of the myosin ATPase vanadate. The caffeine concentration dependency of respi ration of fibers coincided with the caffeine-caused stimulation of myo sin ATPase activity. The activation of oxidative phosphorylation in sa ponin-skinned human muscle fibers by caffeine can be explained by a st imulation of myosin ATPase caused by Ca2+ release from sarcoplasmic re ticulum.