The influence of BPA on isometric contraction, cholinergic activity, and antioxidant status in the crop gizzard of Lumbricus terrestris

The billions of tons of bisphenol A (BPA)-containing waste constitutes a serious concern. BPA leaching from waste through water is a major source of soil contamination. BPA enters the body primarily through ingestion and affects cellular redox balance and cholinergic neuronal activity. The aim of this study was to assess gastrointestinal motility, acetylcholinesterase (AChE) activity, antioxidant enzyme activity (SOD, CAT, and GPx), and the GSH, MDA, and choline (Ch) concentrations in the digestive systems of Lumbricus terrestris earthworms reared for 7 d in soil containing various BPA concentrations. After the 7-d exposure period, crop gizzards were collected from the digestive tracts for analysis. BPA exposure caused an increase in AChE activity, except in animals exposed to the highest BPA concentration. Changes in cholinergic activity were confirmed via Ch concentration measurements. We observed that BPA exerted a relaxant effect on crop gizzard muscles, with statistically significant decreases in the frequency and maximum force of spontaneous isometric contractions (ICs). The IC parameters induced by acetylcholine chloride (AChC) were lower in animals reared in BPA-contaminated soil than in those of the control group. Statistically significant reductions in the mean and minimum IC forces were observed. SOD activity and GPx activity increased in response to low and medium BPA concentrations but decreased in animals exposed to the highest BPA concentration. A similar pattern was observed for the GSH concentration. CAT activity notably decreased in a BPA concentration-dependent manner. Additionally, we observed a statistically significant and BPA concentration-dependent increase in the MDA concentration.