Effects of carbon monoxide on skeletal muscle.

Isometric twitch tension was determined in vitro in rat gracilis anterior muscle during exposure to tyrode's solution at 23.5°C aerated with mixtures of carbogen (95% O2, 5% CO2) and carbon monoxide (CO). Twitch tension was determined once every second. Decrease in tension over time as a function of hypoxia and hypoxia induced by CO was determined. Sixty muscles were studied. The onset of fatigue was accelerated when hypoxia was produced by CO and O2 mixtures in comparison with low O2 alone. Under anoxic conditions, the fatigue rate was nearly doubled by the presence of 100% CO. Recovery from fatigue in the presence of 100% carbogen was prolonged after exposure to CO in comparison to anoxia alone. CO can induce muscle fatigue by impairment of CO2 transport at the cellular level. Delayed recovery from CO induced fatigue suggests intracellular binding of CO. The findings are of importance since under conditions of hypoxia, the affinity of CO for myoglobin and several cytochromes may exceed that of hemoglobin.