Abstract: AIM: To study the effect of chmonin onexpression of inducible-nitric-oxide-synthase and CO₂ stitutive-nitric-oxide-synthase in chronic hypoxic hypercapnicrats, and to explore the mechanism of. inhibition on pulmonary hypertension induced by hypoxic hypercapnia.METHODS: Thirty-six Sprague-dawley rats were ran-domly divided into three groups: normal CO₂ group(A), hypoxic hypercapnic group (B), hypoxic hypercapnia chimonin group (C). NO, INOS, CNOS in blood lung homogenate were measured. INOS MRNA and CNOS MRNA was observed in arterioles from rats bthe technique of in situ hybridization. The average valueof integral light density (ID) of INOS MRNA and CNOSMRNA in pulmonary arterioles was detected by an imageanalysor and the relative CO₂ of MRNA and CNOS MRNA was calculated.RESULTS: MPAP was higher in ratsof B group than that of A group and it was much lower inrats of C group than that of B group. Differences of mCAP were not significant in three groups; NO CO₂ncentration inblood serum and lung homogenate in rats of B group were significantly lower than those of A group, and those of Cgroup were significantly higher than those of B group (P< 0.01). The activity of CNOS in blood serum and lunghomogenate in rats of B group were lower than those of Aand C group (P < 0.01). Activity of INOS in blood seand lung homogenate of B group were higher thanof A group (P < 0.01), and there were not signif-cant difference between blood serum INOS in B and Cgroup. C group INOS in lung homogenate were higherthan those of B group (P < 0. 05). Iight microsCO₂py and electron microsCO₂py showed that chimonin reversed the remodeling of pulmonary arterioles induced by hypoxic hypereapnia.CONCLUSION: Chimohin can increase the expression of inducible-nitric-oxide-synthase gene andCO₂nstitutive-nitric-oxide-synthase gene on chronic hypoxichypercapnic rats pulmonary arterioles, and up regulateCNOS/NO system in hypoxic hypercapnic rats may be oneimportant mechanism of the eftect that chimonin inhibithypoxic hypercapnia pulmonary hypertension.

Key words: chimonin, inducible-nitric-oxide-synthase, cnstitutive-nitric-oxide-synthase, anoxia, hypercap-nia, hypertension, pulmonary, gene