EXPOSURE TO CHRONIC HYPOXIA INDUCES QUALITATIVE COLLAGEN IN THE WALLSOF PERIPHERAL PULMONARY-ARTERIES

Qualitative changes of vascular wall matrix collagens in chronic hypox ic pulmonary hypertension were studied by gel electrophoresis. Male ad ult rats (n = 12) were exposed to hypoxia (F-iO2 = 0.1, 3 wks). Contro l rats (n = 13) were kept in air. Samples of peripheral pulmonary arte ries (PPA, diam. 100 - 400 mu m), main branches of pulmonary artery, a nd aorta were dissected. Arterial samples were treated with 4M guanidi ne-HCl to remove noncollagenous moieties and the collagenous stroma wa s dissolved by limited pepsin digestion at low pH. Low molecular mass peptides (M. W. approx. 76 and 66 kD) were detected in the gel electro phoretic profile of collagen peptides of PPA of the chronically hypoxi c animals and in aorta of both hypoxic and normoxic groups. These pept ides were absent in the PPA of normoxic rats. Since the 76 kD peptide bound anticollagen type I antibodies, it appears to be of collagenous nature and it may be the result of collagenolytic activity in PPA isol ated from hypoxic lungs. This was confirmed by zymography. We conclude that exposure of rats to chronic hypoxia results in the presence of l ow molecular mass peptides in the wall matrix of PPA which resemble th ose found in aorta of normoxic animals. Collagenolytic activity in the walls of peripheral pulmonary arteries may participate in the mechani sm of lung vascular remodelling in chronic hypoxia.