Objective: Thymol is known to cause smooth muscle relaxation, possibly by inhibition of Ca2+influx, release or loss of its sensitivity. It is, however, also reported to be a strong antioxidant in several other systems. In this study, we investigate other possible pathways of thymol caused relaxation of aortic and tracheal segments by using specific blockers, and explore it as potential ameliorator of arsenic and mercury caused hyper contraction.Methods: Male Wistar rats were used in all experiments. Aorta/trachea was carefully removed, cleaned, and cut into 2-mm thick rings. Isometric contractions were measured using organ bath system. One-way analysis of variance (ANOVA) and Student's t-test were used for statistical analyses. P<0.05 was considered significant.Results: In pollutant unexposed aortic and tracheal segments, thymol is found to inhibit contractions through quenching of reactive oxygen species (ROS) in addition to its previously reported effects on Ca2+movements. Equal effectiveness in absence and presence of NG-nitro-L-arginine methyl ester (L-NAME) indicates that nitric oxide (NO) has no significant role in the thymol caused relaxation.Conclusion: In both muscle types, thymol is found to be an effective ameliorator of As (III) and Hg (II) caused hyper contraction, at low concentrations; it acts by inhibiting the Ca2+influx whereas at high concentration, it acts by blocking Ca2+influx and neutralizing ROS.Â
