Evidence for improved myocardial oxygen delivery and function during hypoxia in the mole rat

The high capillary density of the hypoxic adapted mole rat may provide an efficient oxygen extraction system that permits the maintenance of a normal metabolic rate during hypoxia. We compared myocardial function and energetics in the isolated working heart of the mole rat with that of the white rat during oxygenation (567 torr O2) and 3 hypoxic periods of 319, 232 and 155 torr O2, each followed by a reoxygenation period. Control hearts were perfused for a similar time but with oxygenated buffer. The control oxygenated mole rat heart had higher coronary flow (CF), systolic pressure and myocardial O2 consumption (VO2) and lower coronary resistance compared with the heart of the white rat. The hypoxic heart of the mole rat had higher CF, aortic flow, stroke volume, VO2, mechanical power and efficiency, and lower coronary resistance compared with the hypoxic heart of the white rat. The better performance of the hypoxic mole rat heart was not due to a more efficient O2 extraction but was associated with a lower coronary resistance. The findings correlate with the known cardiac physiology of the intact mole rat.