Constant daily hypoxia leads to different degrees of pulmonary hypertension in two different rat strains

Pulmonary diseases associated with diurnal hypoxemia are known to be associated with pulmonary hypertension in some patients. In this study we examined the effects of daily hypoxia (10% oxygen; 8h/day for 14 days) on two strains of rats to simulate sleep related hypoxia in pulmonary diseases expecting to find differences in vascular responses, the develop-ment of right ventricular hypertrophy and pulmonary hypertension according to genetic background. In response to daily hypoxia, Sprague Dawley rats developed right ventricular hypertrophy while Brown Norway rats did not. Both strains developed pulmonary hypertension (elevated right ventricular pressure) although the increase was significantly greater in the Sprague Dawley strain. Pulmonary artery (first branch) vasoconstrictive responses to potassium chloride were increased equally in both strains and the subsequent vasodilation with acetylcholine were reduced equally with daily hypoxia in both strains. Taken together, these findings suggest that the genetic makeup of the rats contributed significantly to the development of right ventricular hypertrophy and the degree of pulmonary hypertension. Moreover, this response is not secondary to differences in the intralobar pulmonary vascular reactivity. Genetic background could explain why certain patients do worse with hypoxia inducing pulmonary vascular diseases.