AimTo explore the effect of tobacco smoke on hydrogen sulfide (H₂S)/cystathionine-γ-lyase (CSE) system in rat thoracic aorta.Methods10-week-old SD rats for the study were randomly divided into control group, short-term smoking group, mid-term smoking group and long-term smoking group.Passive cigarette smoking rat model was established by the method of tobacco smoked suction.The concentrations of H₂S in the serum was measured with sensitive sulfur electrode.The expression of CSE in the thoracic aortic smooth muscle was observed with the methods of immunohistochemical staining and quantitative microscopic image analysis.ResultsH₂S concentration between short-term smoking group and control group had no significant difference (p>0.05).H₂S concentration of long-term smoking group and mid-term smoking group were respectively lower than that of the control group and short-term smoking group (p<0.01).H₂S concentration of long-term smoking group was significantly lower than that of the mid-term smoking group (p<0.05).The concentration of H₂S reduced with the extension of time of tobacco smoke suction and was time-dependent.The CSE expression in the thoracic aortic between short-term smoking group and control group had no significant difference (p>0.05), expression in long-term smoking group and mid-term smoking group were respectively lower than in control group and short-term smoking group (p<0.05), and in long-term smoking group was significantly lower than in the mid-term smoking group (p<0.05).The CSE and SUR-2 expression reduced with the extension of time of tobacco smoked suction, and was time-dependent.ConclusionsTobacco smoke can significantly lower H₂S content in the rat serum and CSE expression in the rat thoracic aorta.