THE BURNlNG OF CARBON MONOXIDE BY HEART AND SKELETAL 1MUSCLE

In a previous paper (1932) we have described experiments indicating that in an intact frog muscle the metabolism is increased between 2 and 3 times when the air surrounding the muscle is replaced by a mixture of 21 per cent 02 and 79 per cent CO. The purpose of the present paper is to extend these observations to other tissues of both cold and warm-blooded animals and to show that this increased metabolism is not merely an increase in the normal metabolism but rather a CO metabolism in which CO is burned to CO2 by the consumption of oxygen. The important fact emerges from these experiments that it is only in muscle tissue, either heart or skeletal, that this stimulation of metabolism or the burning of CO can take place to any important extent. The significance of this fact is not at present clear. SERIES I. THE EFFECT OF CO ON DIFFERENT TISSUES. Method: The general technique employed for the oxygen consumption measurements of series 1 has already been described. For the particular experiments herein reported it may be stated that two differential volumeters are used in which are placed two comparable pieces of tissue. In one respirometer is put a mixture of 02 and CO containing 21 per cent 02 and, in the other, air. The oxygen tension is therefore the same in both and is adequate to meet the demands of the tissue. Oxygen consumption measurements are then made for 2 to 3 hours after which the gases in the two respirometers are interchanged. The oxygen consumption rates are again measured for a similar period of time. At least 1 hour is allowed before the final rates are obtained which are used in tabulating the results. In muscle t)here seems to be no after effect due to the period of CO so it seems permissible to average together the two rates so obtained in CO for comparison with the two rates obtained in air. Thus instrumental errors and random differences between the two samples are ruled out. The experiments were all carried on at 22°C. on frog, turtle, and rat tissues. The frogs were Rana pipiens or R. clamitans and the turtles most,ly Pseudomys elegans. ResuZts. By means of the technique described we have made measure-