The anticholinesterase effect of the cotton defoliant S,S,S-tri-n-butyl phosphorotrithioate (DEF) on channel catfish

The anticholinesterase activity of the organophosphorus cotton defoliant DEF towards channel catfish was investigated using in vivo and in vitro techniques. Acetylcholinesterase (AChE) activity and tissue concentrations of DEF were determined during and following 96 h exposures of catfish to a sublethal dose of DEF using aerated, static aquaria. The results indicated a progressive decrease in brain and muscle AChE activity during the exposure, but the maximum anticholinesterase effect occurred several days following transfer to DEF-free aquaria. However, maximum tissue concentrations of DEF typically occurred at 48 h of exposure, suggesting that DEF undergoes metabolic activation. In vitro incubations of DEF with catfish brain tissue indicated that parent DEF does not interact with brain AChE. Inclusion of a microsomal activation system in the incubation mixture indicated that DEF is converted into a potent anticholinesterase agent by rat liver and catfish liver microsomes. Activation is dependent on oxygen and is primarily mediated by cytochrome P-450. © 1988.

Duke Scholars

Author Richard T. Di Giulio Environmental Sciences and Policy