Korean J Anesthesiol Lee, et al. Fig. 4. Effect of low doses of procaine (P-5: 10-5, P3x-5: 3 × 10-5, P-4: 10-4 M) on the reactive oxygen species (ROS) attack. Data are presented as mean ± SE. ACh: acetylcholine, EL(-): before electrolysis. *P < 0.05, compared with ACh 10-7 to 10-6 M of EL(-), †P < 0.05, compared with the procaine 10-5 M (P-5) group. Fig. 6. The antioxidant effect of the lidocaine 3 × 10-3 M (L3x-3+) group is not attenuated by the pretreatment of 3AT (L3x-3+AT). Data are presented as mean ± SE. Before electrolysis: L3x-3-, L3x-3-AT. ACh: acetylcholine. 3AT: 3-Amino-1,2,3-Triazole. Fig. 5. Effect of high doses of procaine (P3x-4: 3 × 10-4, P-3: 10-3, P3x-3: 3 × 10-3 M) on the reactive oxygen species (ROS) attack. Data are presented as mean ± SE. ACh: acetylcholine, EL(-): before electrolysis. †P < 0.05, compared with ACh 10-7 to 10-6 M of the procaine 10-5 M (P-5) group. Fig. 7. The antioxidant effect of the procaine 3 × 10-3 M (P3x-3+) group is significantly attenuated by the pretreatment with 3AT (P3x- 3+AT). Data are presented as mean ± SE. Before electrolysis: P3x-3-, P3x-3-AT. ACh: acetylcholine. 3AT: 3-Amino-1,2,3-Triazo*lPe.< 0.05, compared with the procaine 3 × 10-3 M (P3x-3+) group. Similarly, procaine dose-dependently reduced the relaxation induced by ACh when compared with that before the ROS exposure (P < 0.05, Fig. 4 and 5). Effect of 3AT on the endothelial injury by ROS 3AT with lidocaine did not affect lidocaine activity (Fig. 6), but did reduce the relaxation induced by 10-6 M ACh after procaine pretreatment (P < 0.0141, Fig. 7). www.ekja.org Discussion We generated ROS by direct EL of a physiologic salt solution (PSS), such as the K-H solution [8], and the other researchers are directly injecting H2O2 to PSS [13]. ROS such as O2., H2O2, and OH. are generated during PSS EL [14-17]. We did not add normal levels of ascorbic acid (1.1 × 10-4 M) to exclude its anti- oxidizing effect. A number of tiny air bubbles were generated at the positive and negative electrodes when the electric current was applied. In mouse thoracic aorta, 5 minutes of EL 107