Mitochondrial function in the presence of myoglobin

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Abstract
The effect of myoglobin on O2 consumption and ATP production by isolated rat skeletal muscle mitochondria was studied under steady-state conditions of O2 supply. A method is presented for the determination of steady-state O2 consumption in the presence of O2-binding proteins. O2 consumed in suspensions of mitochondria was replenished continuously by transfer from a flowing gas phase. Liquid-phase O2 pressure was measured with an O2 electrode; the gas-phase O2 concentration was held constant at a series of fixed values. O2 consumption was determined from the characteristic response time of the system and the difference in the steady-state gas- and liquid-phase O2 concentrations. ATP production was determined from the generation of G-6-P in the presence of hexokinase. During steady-state mitochondrial O2 consumption, the O2 pressure in the liquid phase in enhanced when myoglobin in present. Functional myoglobin present in the solution had no effect on the relation of mitochondrial respiration and ATP production to liquid-phase O2 pressure. Myoglobin functions in this system to enhance the flux of O2 into the myoglobin-containing phase. Myoglobin may function in a similar fashion in muscle by increasing O2 flux into myocytes.