[Contractile function and the effectiveness of oxygen utilization by the heart during adaptation to hypoxia]

Experiments on isolated functioning hearts of rats established that under equal filling pressure the hearts of the animals who are adapted to the periodic effect of hypoxy develop a higher force and rate of contractions; ultimately, the contractile function of such hearts, as calculated per unit of myocardial mass and unit of time, appears to be increased by 1/3. Oxygen consumption by the hearts of adapted animals does not much differ from the control values, and consequently, the efficiency of oxygen utilization increases approximately by 1/3. A considerable increase of adrenoreactivity of the hearts of adapted animals is also noted. The obtained data are discussed proceeding from the assumption that an increased power of the potassium pump in the sarcoplasmatic reticulum of the myocardium of adapted animals may influence the coupling of oxydation with phosphorillation in the mytochondria.