Pulmonary vascular response of the coati to chronic hypoxia

The unusually muscular pulmonary arteries normally present in cattle and sw ine residing at low altitude are associated with a rapid development of sev ere pulmonary hypertension when those animals are moved to high altitude. B ecause these species lack collateral ventilation, they appear to have an in creased dependence on hypoxic vasoconstriction to maintain normal ventilati on-perfusion balance, which, in turn, maintains thickened arterial walls. T he only other species known to lack collateral ventilation is the coati, wh ich, similarly, has thick-walled pulmonary arteries. We tested the hypothes is that coatis will develop severe high-altitude pulmonary hypertension by exposing six of these animals (Nasua narica) to a simulated altitude of 4,9 00 m for 6 wk. After the exposure, pulmonary arterial pressures were hardly elevated, right ventricular hypertrophy was minimal, there was no muscular ization of pulmonary arterioles, and, most surprising of all, there was a d ecrease in medial thickness of muscular pulmonary arteries. These unexpecte d results break a consistent cross-species pattern in which animals with th ick muscular pulmonary arteries at low altitude develop severe pulmonary hy pertension at high altitude.