Evaluation of Sublethal Effects of Dichlorvos upon Caenorhabditis elegans Based on a Set of End Points of Toxicity

The primary objective of this study was to examine a possible correlation among the three endpoints of toxicity, namely, stress gene expression (hsp16), feeding, and acetylcholinesterase (AChE) activity in transgenic C. elegans (hsp16-lacZ) exposed to sublethal concentrations of dichlorvos, an organophosphorus insecticide. Worms exposed to dichlorvos (at 5, 40, and 80 mu M) exhibited a concentration-dependent inhibition in feeding with total cessation in feeding occurring beyond 4 h of exposure. Concomitantly, marked and dose-dependent inhibition (69%-90%) of AChE was also evident after 4 h of exposure. Induction of heat shock protein (Hsp) was evident after 4 h of exposure (as seen from quantitative analysis), although maximum expression of Hsp was evident only after 24 h of exposure (as evident from qualitative analysis). Interestingly, the Hsp induction was restricted only to the pharyngeal region. Significant correlation was discernible between the three evaluated end points suggesting their possible interrelated role in the physiological dysfunctions evoked by sublethal concentrations of dichlorvos. (C) 2009 Wiley Periodicals, Inc. J Biochem Mol Toxicol 23:9-17, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10:1002/jbt.20258