[Effect of oxygen supply on isolated rat heart energetics]

The total energy expenditure of the rat isolated heart and the external work of the preparation are positively correlated with the oxygen supply of the heart. A positive partial correlation was revealed between the total energy expenditure of the heart and the oxygen supply of the heart at constant external work of the heart which means that the heart efficiency coefficient decreases on an increase in the oxygen supply. By means of calculation of the partial regression of the heart total energy expenditure on external work at a constant oxygen supply, the "pure" efficiency coefficient of the heart (i. e. the ratio between an increment in the heart work and the corresponding increment of the total energy expenditure of the heart) was found to be about 41 per cent on the average.