A Comparison between The Effect of Sub-lethal Doses of Atraz,ine and DDT on Brain and Plasma Acetylcholinesterase of the African Catfish (Clarias gariepinus)

The effect of in vivo exposure to two sublethal concentrations of atrazine and one concentration of DOT on acetylcholinesterase in brain and plasma of the fresh water fish Clarias gariepinus was measured. BloQd and brain were taken after various periods of exposure (3-168 hr for atrazine and 3-24 hr f9r DOT). Controls were treated parallel. A real inhibition of brain AChE specific activity was detected by exposure hr 6 at the lower atrazine concentratiolI and by exposure hr 9 at the higher concentration. The remain<!er of changes were considered false due to changes in brain water content and/or protein content. The effect of DOT was restricted to a real activation only by exposure hr 6. Plasma AChE specific activity increased throughout the whole experimental time during exposure to the lower concentration of atrazine, while reduction was recorded in the beginning and toward the end of experiment at the higher concentration. Plasma AChE activity during DOT exposure ranged froni initial decrease followed by increase, then inhibition and finally activation which could give an indication that DOT is more harmful than atrazine at its higher concentration (500 jJ.g/1). Although the changes are clear in the enzyme activity of the brain, plasma AChE seems to be more useful as a monitor of exposure to anticholinesterase chemicals.