Increasing effect of caffeine on the oxygen consumption of the skeletal muscle.

Abstract

The changes of metabolic activity of the skeletal muscle at various concentrations of caffeine were observed in connection with the mechanical change of the muscle.1. At high concentrations of caffeine, mechanical change of the muscle was detected but the change of the oxygen consumption was not recognized. At low concentrations of caffeine, on the other hand, the quite opposite results were obtained, i. e. the oxygen consumption was increased but no mechanical change was observed.2. In the K-depolarized muscle, 5mM caffeine increased the oxygen consumption of the muscle as in the case of the normal muscle.3. Caffeine did not stimulate the respiration of the muscle homogenates and the muscle mitochondria.4. Lactic acid content of caffeinized muscle increased with the increase of the concentrations of caffeine.5. In the IAA-poisoned muscle, caffeine exhibited the increasing effect of the oxygen consumption as observed in the normal muscle.6. The content of various phosphate compounds, CrP, ATP and ADP, decreased with the increase of the concentration of caffeine. On the other hand, inorganic phosphate (Pi) increased with the increase of the concentration of caffeine, in the range of concentration less than 5mM and decreased with the increase of the concentration of caffeine, in the range of concentration over 5mM.Based on these results, it was suggested that, through a certain mechanism, various metabolic processes were stimulated by low concentrations of caffeine without any mechanical change.