Oxygen consumption and substrate uptake of the hypertrophied rat heart in situ.

A new heart preparation was developed which permits in situ measurements of myocardial oxygen consumption and substrate uptake in small animals. Using the new method the mechanical activity, as well as oxygen consumption and substrate uptake of the heart, was measured in Goldblatt rats with left ventricular hypertrophy of about 40%. 1. In agreement with former investigations on the hypertrophied rat heart, this model also shows that both the performance of the whole ventricle, as well as the contractile force per unit of cross-sectional area, is increased in the state of stable hypertrophy. 2. The absolute values of oxygen consumption and substrate uptake are increased in the hypertrophied hearts. However, oxygen consumption and substrate uptake as related to muscle mass and to wall stress were largely identical in hypertrophied and control hearts. 3. Hypertrophied hearts and controls utilize substrates according to their respective arterial blood concentration. Under our experimental conditions approximately 50% of the total energy in both groups is obtained from glucose, 30% from lactate, and 20% from fat. The relatively high consumption of lactate could be explained by the glucose uptake and lactate release of the erythrocytes.