Sumitra Arora
ICAR-National Research Centre for Integrated Pest Management, India
Title: Potentiation of toxicity of organophosphate pesticides in mixtures
Biography
Biography: Sumitra Arora
Abstract
Anticholinesterase inhibiting insecticides are likely to co-occur in environment as mixtures. This raises the possibility of antagonistic, additive, or synergistic neurotoxicity in exposed organisms. Acetylcholinesterase (AChE) inhibition has been demonstrated to be a useful biomarker for exposure to organophosphorous (OP) insecticides in many environments. The objective of this study was to investigate the response of housefly (Musca domestica) head AChE (HF-AChE) exposed to five OPs as individual compounds and their binary mixtures under in vitro conditions. To examine the effects of oxidation on OP potency in the HF-AChE system, bromine water was used as an oxidizing agent. The sensitivity of HF-AChE increased significantly to oxon analogues of chlorpyrifos (CPF), malathion (MLT) and triazophos (TRZ). Monocrotophos (MCP) and profenofos (PRF) did not exhibit any significant differences in toxicity under oxidised and un-oxidized conditions. The concentration addition model, the combination index–isobologram equation and the toxic unit approach, all three models, provided similar predictions for toxicological interaction of 10 binary combinations of OPs under oxidized and un-oxidized conditions. The antagonistic effects of the binary combination of OPs (CPF+PRF, CPF+MLT, MCP+MLT, PRF+MLT, MLT+TRZ and PRF+TRZ), was observed under oxidized conditions. This may be due to dispositional and/or receptor antagonism. Most of the binary combinations under un-oxidized conditions exhibited synergistic responses. Triazophos showed very strong synergism in binary combinations with CPF, MCP and PRF. Contrarily only CPF+TRZ exhibited synergism under oxidized conditions. The results indicated differential toxicity of binary combinations of OPs under oxidized and un-oxidized conditions.