EXCESS COLLAGEN IN HYPERTENSIVE PULMONARY-ARTERIES DECREASES VASCULARDISTENSIBILITY

Increased Vascular collagen content is a major feature of pulmonary va scular remodeling. The functional role of excess collagen in decreasin g pulmonary vascular compliance has not been established. We determine d whether there was a correlation between hydroxyproline content of ra t pulmonary artery segments and elastance (E(PA)) of the pulmonary art ery bed during development of hypoxic pulmonary hypertension (10% O-2, 10 d) and normoxic recovery. E(PA) was measured by air-filled pressur e-volume curves. After 10 d of hypoxia, hydroxyproline content increas ed approximately 2-fold in large segments (1,200-250 mu m in diameter) but not significantly in small segments (> 250 mu m). Elastance incre ased from 87 +/- 6 (SEM) to 145 +/- 8 mm Hg/ml (p < 0.05) within 5 d o f hypoxia and returned to control value 3 wk after recovery. There was a correlation between collagen content and E(PA) in large segments du ring development of hypertension; no correlation was found during reco very from hypoxia. The ratio of hydroxyproline to total protein was un changed in large segments after recovery from hypoxia but was increase d in small segments after recovery. We conclude that increased collage n in large pulmonary arteries directly influences E(PA) during the dev elopment of hypoxic pulmonary hypertension.