PULMONARY ARTERIAL SMOOTH-MUSCLE CONTRACTILITY IN HYPOXIA-INDUCED PULMONARY-HYPERTENSION

The highly compliant low-resistance pulmonary vasculature is markedly altered with chronic hypoxia. Remodeling in response to hypoxia and/or hypertension involves hypertrophy and hyperplasia of smooth muscle an d excessive deposition of connective tissue that likely contributes to the maintenance or exasperates the already elevated pulmonary arteria l (PA) pressure. The purpose of this study was to investigate the effe ct of chronic hypoxia on the contractile properties of PA smooth muscl e. Isometric and isotonic experiments were performed on excised PA rin gs from pulmonary hypertensive (induced by 14 days of hypoxia) Sprague -Dawley rats. A doubling of the vessel wall thickness occurred during the development of hypoxia-induced pulmonary hypertension. Functionall y, there was a decrease in isometric stress (force to cross-sectional area ratio). No difference was detected in the velocity of shortening or in total shortening ability. This study provides evidence that, in addition to the morphological changes, changes in PA smooth muscle con tractility also appear to play a role in the development and/or mainte nance of hypoxia-induced pulmonary hypertension.