Alterations on AChE activity of the fish Anguilla anguilla as response to herbicide-contaminated water

The inhibition of both total and specific acetylcholinesterase activities was measured in the whole eyes of the yellow eel Anguilla anguilla after exposure to the carbamate thiobencarb. In vivo assays were conducted under a constant flow-through system of thiobencarb-contaminated water (1/60 LC(50) 96 h=0.22 ppm for 96 h) followed by a recovery period in clean water (192 h more). The results indicated a measurable level of AChE activity on eyes of control eels, which resulted in a sensitive indicator of the presence of thiobencarb in the water. The pesticide induced significant inhibitory effects on AChE activity ranging from 35% in total AChE activity to 75% in specific AChE activity. Following 1 week of recovery, AChE activity in eel eyes was still different from that of controls. Specific AChE activity remained significantly depressed (35%). On the other hand, protein content in whole eyes of pesticide-treated eels did not exhibit any significant difference from control animals. It has been accepted that a minimum of 20% reduction in brain AChE would be necessary to be indicative of exposure to anticholinergic agents; however, few data are reported about this effect on sense organs.