Dose and Time-dependent Alterations in Various Cholinergic and Non-cholinergic Markers after Organophosphate Poisoning: Possible Role in Diagnosis

Toxicity of organophosphates (OP) is mainly ascribed to inhibition of acetylcholinesterase (AChE) enzyme at the cholinergic synapses. This results in cholinergic crisis leading to various muscarinic, nicotinic and central effects. Additionally, there are several non-cholinergic effects of OP which are likely to exacerbate the toxicity and complicate diagnosis. The present study reports the dose (0.125 - 4.0 LD50) and time (1 h - 14 d)- dependent acute effect of diisopropyl phosphorofluoridate (DFP) on mice body weight, organ-body weight index (brain), butyrylcholinesterase (BChE) and β-glucoronidase (BG) activity in plasma, AChE activity, reduced glutathione (GSH) and malondialdehyde (MDA) levels in brain, and DNA damage in brain (agarose gel electrophoresis) and blood (comet assay). The study reveals a dose and time- dependent BChE inhibition up to 24 h and AChE inhibition up to 7 d. However, elevated BG levels were observed up to 1 h only after 1.0, 2.0, and 4.0 LD50 DFP. Diminished GSH levels up to 24 h and increased MDA levels at 4 h indicated oxidative stress. None of the treatments produced any DNA damage in soft tissues. In addition to cholinesterase, the study suggests possible relevance of measuring BG levels (non-cholinergic marker) in the diagnosis of OP poisoning.