Impact of methyl parathion toxicity and eserine inhibition on acetylcholinesterase activity in tissues of the teleost (Tilapia mossambica)--a correlative study.

Acetylcholinesterase (AChE) activity and acetylcholine (ACh) content of muscle, gill, liver and brain tissues of control and methyl parathion-exposed (MPE) fish were determined. In addition, in vitro concentrations of eserine necessary to produce inhibition of AChE equivalent to in vivo inhibition by sublethal amounts of methyl parathion (MP) were also investigated. AChE activity decreased in all tissues, while ACh content showed a corresponding increase. These observations indicate disruption of nerve impulse conduction. The in vitro effect of eserine on AChE activity differed with the type of MP action. These results are discussed in relation to the sensitivity and extent of innervation of various tissues.