Prolonged exposure to alveolar hypoxia induces physiological changes in the pulmonary
vasculature that result in the development of pulmonary hypertension. A hallmark of hypoxic
pulmonary hypertension is an increase in vasomotor tone. In vivo, pulmonary arterial smooth
muscle cell contraction is influenced by vasoconstrictor and vasodilator factors secreted from
the endothelium, lung parenchyma and in the circulation. During chronic hypoxia,
production of vasoconstrictors such as endothelin-land angiotensin II is enhanced locally in …