Aim:To investigate the role of the endogenous cystathionine γ-synthase(CSE)/hydrogen sulfide(H2S)pathway in vascular calcification in vivo.Methods:A rat vascular calcitication model was established by administration of vitamin D3 plus nicotine(VDN).The amount of CSE and osteopontin(OPN)mRNA was determined by using semi-quantitative reverse-transcription polymerase chain reaction.The calcium content,45Ca2+ accumulation and alkaline phosphatase(ALP)activity were measured.H2S production and CSE activity were measured.Results:von Kossa staining produced strong positive black/brown staining in areas among the elastic fibers of the medial layer in the calcified aorta.The calcium content,45Ca2+ accumulation and ALP activity in calcified arteries increased by 6.77-,1.42-,and 1.87-fold,respectively,compared with controls.The expression of the OPN gene was upregulated(P＜0.01).Expression of the CSE gene was downregulated.However,calcium content.45Ca2+ uptake and ALP activity in the VDN plus NaHS group was lower than that in the VDN group.The content of calcium and 45Ca2+ accumulation and activity of ALP in the aorta were 34.8%,40.75%and 63.5%lower in the low-dosage NaHS group than in the VDN group,respectively(P＜0.01),and the calcium content and deposition of 45Ca2+ and activity of ALP was 83.9%,37.8%and 46.2% lower in the aorta in the high-dosage NaHS group than in the VDN group,respectively(P＜0.01).The expression of the OPN gene was downregulated.Conclusion:The production of H2S,and CSE activity were decreased and CSE gene expression was downregulated in rats with vascular catcification.H2S can ameliorate vascular calcification,suggesting that the H2S/CSE pathway plays a regulatory role in the pathogenesis of vascular calcification.