This study examined the effects of training on intrinsic vasorelaxation and vasoconstriction properties of pulmonary hypertensive rat arteries. Fifty seven male Wistar rats were randomly assigned to 4 groups: normotensive sedentary (n = 14), normotensive trained (n = 15), pulmonary hypertensive sedentary (n = 15) and pulmonary hypertensive trained (n = 13). Pulmonary hypertension was obtained using a chronic hypoxia exposure model. Endothelium-dependent vasorelaxation to acetylcholine (10(-8)-10(-4) M), endothelium-independent vasorelaxation to sodium nitro-prusside (10(-8)-10(-4) M), and vasoconstriction to epinephrine (10(-9)-10(-4) M) and endothelin-1 (10(-12)-10(-7) M) were assessed on isolated rings of large pulmonary arteries. Alterations in endothelium-dependent and -independent vasorelaxation properties as well as enhanced vasoconstrictor responses were obtained in pulmonary hypertensive rats. Chronic exercise did not affect those pulmonary vasoreactivity alterations. A predominant effect of chronic hypoxia over training seems to be partially responsible for this phenomenon, probably through impairment in nitric oxide bioavailability and vascular smooth muscle sensitivity.