Potentiation of the contraction of duodenal visceral smooth muscle in rat through oxidative stress induced inhibition of AChE activity by Methylparaben

Abstract

Methylparaben, a synthetic chemical, is used as preservative to enhance the lifespan of different food items to be stored. So, humans are often exposed to methylparaben through foods preserved with methylparaben. The aim of the study was to examine the effect of methylparaben on contractile function of duodenum, the initial part of small intestine, which helps in digestion and absorption of ingested food. In our study, we have found significant increase in amplitude and frequency of the contraction of duodenum ex vivo in rats exposed to methylparaben dose dependently for all exposure durations in comparison with contraction of the duodenum of rats exposed to DMSO (vehicle control). Significant inhibition of the enzymatic activity of acetylcholinesterase (AChE) in duodenal smooth muscle of exposed rats has also been observed dose dependently in all exposure durations. These results suggest that methylparaben promotes the contraction of duodenum probably by potentiating the contraction of duodenal visceral smooth muscle (VSM). The methylparaben induced potentiation of duodenal VSM might be due to inhibition of AChE activity. The activities of antioxidant enzymes (GPx and GR) have significantly decreased and LDH activity and malondialdehyde (MDA) level have significantly increased in smooth muscle homogenates of rats exposed to methylparaben in our study. These observations suggest that methylparaben inhibits the AChE activity probably by producing oxidative stress in smooth muscle cells. In conclusion, methylparaben potentiates the contractile function of duodenal VSM probably by promoting oxidative stress induced inhibition of AChE activity at myoneural junctions.