Using
potassium channel blockers and openers,the responses of pulmonary vasoconstriction were investigated in rats under
the conditions of chronic hypobaric hypoxia (mimic 5000 m altitude over sea level). The systolic and distolic
pulmonary artery pressure were significantly increased in rats sustained hypoxia for 10 days and 20 days. After 20 days hypoxia,the pulmonary artery perfusion pressure (PMP) and pulmonary vascular resistance ( PVR) in isolated rat lungs were 17.2±2.2 mmHg vs 13.5±2.2 mmHg in normoxia group(P<0. 01) and 1.58±0.30 mmHg. min/ml vs 1.05±0.15 mmHg,min/ml(P<0.01) respectively. And increasing PAPP and PVR by KCl 10～15 mm0l/L were also intensified in hypoxia group.The effects of KCl 10～15 mmol/L on tension of isolated pulmonary artery rings were enhanced by 20days hypoxia with the effect of norepinephrine being unchanged.The effects of potassium channel blocker CsCl 20mmol/L on increasing tension induced by KCl 10～15 mmol/Lwere enhanced in normaxia group,but not in hypoxia group.In contrast,potassium channel opener cromakalim 0.1μmol/L and nicorandil 1μmol/L reduced the increase in PAPP and PVR by KCl in both normaxia and hypoxia groups.Cromakalim and nicorandil also alleviated the increase in tension of isolated pulmonary artery rings by KCl.These results demonstrate that sustained hypoxia affects potassium channels,which is associated with formation of
pulmonary hypertension.