Abstract： Objective To investigate the impact of sodium tanshinone Ⅱ A sulfonate (STS) on interleukin-6(IL-6) expression in rat models with hypoxic pulmonary hypertension (HPH).Methods The SD rats (n=32) were randomized into normoxic control group (group A),hypoxia model group (group B),low dose ( 10 mg· kg-1 · d-1 )of STS intervention group (group C ) and higb dose (30 mg· kg-1· d-1 )of STS group (group D) (n=8 each).The group A was fed in normoxic cabin,while the rats of group B,C and D were put into the atmospheric hypoxjc cabin,with the oxygen concentration of atmospheric hypoxic cabin being(10± 1)％.On one hand,10 mg/kg and 30 mg/kg STS were intraperitoneally infused into group C and group D at 1 d after hypoxia respectively.On other hand,the same dose of saline was intraperitoneally infused into group A and group B.After successive feeding of 21 d,right ventricular systolic pressure (RVSP) and mean arterial pressure (mPAP) were detected in rats of each group by right cardiac manometric method,the vascular morphology and inflammatory response observed by hematoxylin- eosin (HE) staining,IL- 6 component in serum measured by ELISA,and the IL-6 expression detected by real-time fluorescent quantitative PCR.Results The hypoxia significantly induced the increases of RVSP and mPAP.Nevertheless,the increasing levels of RVSP and mPAP were obviously decreased after intervention of STS.The mPAPs were (12.922±0.442) mm Hg( 1 mm Hg=0.133 kPa),(26.737±2.222) mm Hg,( 19.948±1.681 ) mm Hg and(18.547± 1.090) mm Hg in A,B,C,D groups,and RVSPs were (24.677 ± 1.725) mm Hg,(63.675±5.283) mm Hg,(49.250±3.816) mm Hg and (41.839±3.993) mm Hg respectively.STS could improve the vascular morphology and inflammatory response in rats with HPH.Compared with group B,group C and group D had reduced thickening of small arterial wall and smooth muscle layer,narrowing lumen and less lymphocytes and neutrophil infiltration in peripheral vessels.However,the inflammatory response in group C and group D remained obvious as compared with that in goup A.After hypoxia induction,the IL-6 component in group B was significantly elevated as compared with that in group A (P＜0.05).While after intervention of STS,the IL-6 components in group C and group D were lowered as compared with those in group A and group B(all P＜0.05),with IL 6 component in group C higher than that in group D(P＜0.05).Hypoxia significantly induced the expression of IL-6 mRNA in hung tissues,while STS obviously inhibited the expression of IL-6 mRNA.However,the expression levels in these groups were still higher than that in normoxic control group,with group B＞ group C＞ group D＞ group A (all P＜0.05).Conclusion STS is effective in treatment of chronicity HPH caused by hypoxia,which may be correlated with its inhibiting effects on IL-6.