Fig. 2. The H₂S-induced relaxation of rat aortic rings and the underlying mechanisms. (A) Relaxation of the PHE-precontracted tissues by H₂S in the form of either standard NaHS solution (square) or H₂S gas-saturated solution (circle). (B) Inhibitory effect of l-NAME (100 µM, 20 min, circle) on the H₂S-induced relaxation (control, square). (C) The effects of H₂S (180 µM) on the endothelium-free or endothelium-intact aortic tissues pretreated with l-NAME or charybdotoxin (ChTX)/apamin. (D) The relaxant effect of H₂S was not affected by pretreating the tissues with SQ22536, SOD or catalase, respectively. (E) The effect of ODQ treatment (10 µM for 10 min) on the relaxant effects of SNP (0.1 µM) or H₂S (600 µM). n = 8 for each data point. *P < 0.05 compared with control.