Exercise-induced pulmonary vasoconstriction during combined blockade of nitric oxide synthase and beta adrenergic receptors.

Sheep exercised on a treadmill at a speed of 4 mph

Inhibition of NO synthase (N omega-nitro-L-arginine 20 mg/kg i.v.), alpha receptor blockade (phentolamine 5 mg i.v.), beta receptor blockade (propranolol 1 mg i.v.), and combined alpha and beta receptor blockade

Baseline without inhibition/blockade (paired studies)

Blood flow and pressures across the pulmonary circulation (pulmonary vascular resistance and mean pulmonary arterial pressures)surrogate