Differences in time-related cardiopulmonary responses to hypoxia in three rat strains

The cardiopulmonary profile of three rat strains (Sprague-Dawley, Wistar and High altitude-sensitive) was compared upon exposure to hypoxia (9% O2) for 0, 7 or 14 days. No differences were observed among the in vitro contractile (ET-1) and relaxant (carbachol) responses of pulmonary artery isolated from the three strains during normoxia. Chronic hypoxia decreased ET-1 contractile responses and diminished relaxant responses to carbachol similarly in all strains. In Sprague-Dawley, Wistar and High altitude-sensitive rats, pulmonary arterial pressure rose time-dependently and was elevated by 108%, 116% and 167%, respectively, after 14 days of hypoxia compared to normoxic controls. Right ventricular hypertrophy was increased by 51%, 93% and 55%, respectively, at 14 days. Hypoxia-induced hypertrophy and medial thickening in the pulmonary vasculature were more pronounced in High altitude-sensitive rats. Sprague-Dawley exhibited hypoxia-induced airway hyperresponsiveness to intravenous methacholine, but there were no hypoxia- or strain-related differences in in vitro tracheal contractility. Although each strain exhibited greater sensitivity for a particular hypoxia-induced parameter, pulmonary vascular functional and structural changes suggest that High altitude-sensitive rats represent a choice model of hypoxia-induced pulmonary hypertension.