AIM To investigate the effect of ligustrazine on mean pulmonary arterial pressure(mPAP) and nitric oxide synthase (NOS)
in arterioles in chronic hypoxic hypercapnic rats METHODS Thirty rats were randomly divided into three groups: control group(A),hypoxic hypercapnic group(B), hypoxic hypercapnic+
ligustrazine (lig) group (C). Constitutive endothelial NOS (ceNOS) and inducible NOS (iNOS) were observed in arterioles of rats using the technique of immunohistochemistry, ceNOS mRNA and iNOS mRNA were observed by the technique of hybridization in situ RESULTS ① mPAP was
significantly higher in rats of B group than that of A group(P<001) and it was much lower in rats of C group than that of B group (P<001), Differences of mCAP were not significant in three groups (P>005) ; Serum nitric oxide (NO)concentration was significantly higher in rats of C group than that of B group (P<005) ; ②Light microscopy showed WA/TA (vessel wall area/total area) and SMC (the density of medial smooth muscle cells) were significantly lower in rats of C group than that of B group (P<001). Electron microscopy showed that ligustrazine could inhibit the proliferation of smooth muscle cells and collageous fibers of pulmonary arterioles in chronic hypoxic hypercapnic rats③Immunohistochemistry showed the average value of integral light density(LD) of ceNOS in pulmonary arterioles was significantly higher in rats of C group than that of B group(P<001), difference of LD of iNOS in pulmonary arterioles was not significant between B group and C group (P>005); ④Hybridization in situ showed LD of ceNOS mRNA in pulmonary arterioles was significantly higher in rats of C group than that of B group (P<001). Difference of LD of iNOS mRNA in pulmonary arterioles was not significant between B group and C group(P>005) CONCLUSION Ligustrazine can inhibit pulmonary hypertension and the proliferation of smooth muscle cells and collagenous fibers of pulmonary arterioles in chronic hypoxic hypercapnic rats by incresing the expression of ceNOS and ceNOS mRNA in pulmonary arterioles