RESUMEN
A model of hypoxic pulmonary hypertension (HPH) was reproduced in rats by exposing them to chronic hypoxia environment corresponding to 5km level. At 10d,20d, 30d after hypoxia in hypoxia groups and control group, the pulmonary vascular structural changes were observed with optical microscope, histochemistry and electronic microscope. The changes in hypoxia groups were as follows: ①the wall of small pulmonary arteries of every calibre showed marked thickening compared with that in control group, and the main changes involved smooth muscle cells(SMC)proliferation and collagen deposition in the vessels wall; ② SMC proliferation, muscularization of non myocytic arteries and partial myocytic arteries were observed in intra acinar pulmonary arteries, so the counts of muscular arteries significantly increased compared with control group( P