Abstract: Aim The effect of heparin on the changes of pulmonary circulation induced by chronic hypoxia-hypercapnia(HH) in rat was studied. Methods The pulmonary ariery pres-sure, right ventricular pressure, Hct % and the muscularization of pulmonary arterioles (MPA) were examined in rals that were exposured to HH for one month and treated with or without heparin respectively. Results The development of pulmonary hypertension and increase of MPA in HH rats were significantly prevented by heparin, but the increase of MPA was still developed as compared with that in the normal control. Conclusion Heparin can partially prevent pulmonary hypertenvSi'on and muscularization of pulmonary arterioles induced by hypoxia-hypercapnia.

Key words: hypoxia, hypercapnia, pulmonary hypertension, pulmonary circulation, heparin