Biochemical, behavioral, embryotoxic and long-term effects of fenthion as compared to desbromoleptophos and fenitrothion in chicks

The effects of three organophosphorus esters (OP's): desbromoleptophos (DBL), fenitrothion (FTR) and fenthion (FEN) on neurotoxic esterase (NTE), acetylcholinesterase (AChE) and behavior were investigated in young chicks and in chick embryos. FEN was used in both the formulation (SPOTTON{dollar}sp{lcub}rm R{rcub}{dollar}) and the pure form. These compounds were given either as single or multiple doses and either as dermal or oral doses. The effects of these OP's on central and peripheral NTE and AChE inhibition were also compared. DBL, a known delayed neurotoxicant, caused both NTE and AChE inhibition in both the chicks and chick embryos. FTR, a non-delayed neurotoxicant, caused AChE inhibition but no significant NTE inhibition. FEN, which is suspected of being a delayed neurotoxicant, did not inhibit NTE significantly but caused AChE inhibition. Both DBL and FEN significantly altered the gait of both treated chicks and treated embryos but the non-OPIDN inducing FTR did not. Chicks treated with commercial FEN (SPOTTON{dollar}sp{lcub}rm R{rcub}{dollar}) developed an atypical ataxia at the normal age for onset of sensitivity to OPIDN. Both DBL and FEN, injected in ovo, caused paralysis in chick embryos after they hatched. Minimal NTE inhibition, long-latency for the development of ataxia, immaturity of chicks at treatment, absence of any enzyme inhibition at the time of alteration of the gait, and irreversible functional alterations distinguish FEN-induced functional deficits from classical OPIDN. This effect associated with the OP's is different from both the acute (AChE inhibition) and the delayed (NTE inhibition) effects.