AJP - Cell Physiology, Vol 263, Issue 3 C598-C606, Copyright © 1992 by American Physiological Society
Regulation of oxygen consumption in fast- and slow-twitch muscle
M. J. Kushmerick, R. A. Meyer and T. R. Brown
Department of Radiology, University of Washington, Seattle 98195.
Phosphorus nuclear magnetic resonance spectra and steady-state O2
consumption rates were obtained from ex vivo arterially perfused cat biceps
brachii (fast twitch) and soleus (slow twitch) muscles during and after
periods of isometric twitch stimulation at 30 degrees C. In the biceps
muscles, steady-state O2 consumption increased and phosphocreatine (PCr)
concentration decreased progressively with stimulation. PCr recovery after
these stimulation periods followed first-order kinetics with a half time of
10 min. The results in the biceps could be explained by a feedback control
of cellular respiration by ADP concentration. In the soleus, steady-state
O2 consumption also increased and PCr concentration decreased as
stimulation rates increased. The half time for PCr recovery in the soleus
was approximately 5 min, but, in contrast to the pattern in the biceps, the
kinetics was not first order. There was an overshoot during the recovery
period in the PCr content of soleus and a corresponding undershoot of Pi
compared with resting values. Mitochondrial regulation by ADP is not
sufficient to account for respiratory control in slow-twitch soleus. The
respiration rate in neither muscle was dependent on the Pi content. Thus we
conclude that the mechanism of control of cellular respiration is both
quantitatively and qualitatively different in fast- and slow-twitch
skeletal muscle.
