Cholinesterase Activity and Hematological Parameters as Biomarkers of Sublethal Molinate Exposure in Anguilla anguilla

Cholinesterase (ChE) activity was measured in plasma, whole blood [using 5,5′-dithiobis(2-nitrobenzoic acid) and 2-PDS as chromophores], brain, and whole eyes of Anguilla anguilla exposed to a sublethal concentration of 11.15 mg/L (one-third of the 96-h LC50) of the carbamate herbicide molinate. ChE activity was evaluated after 6, 24, 48, 72, and 96 h of pesticide exposure. Results indicated that ChE activity in eel tissues decreased as time of exposure increased, especially in eel blood. Eels exposed to molinate were transferred to a pesticide-free water for a recovery period of 4 days and ChE activity was also evaluated. Results indicated that ChE activity for those animals with preexposure to the carbamate was still different from the controls even after the recovery period. The use of hematological parameters for assessing the toxicity of molinate in A. anguilla was also studied. The parameters included the measurement of blood proteins, hematocrit, hemoglobin, erythrocytes, and leukocytes. Molinate exposure produced a decrease in all the hematological parameters tested, which was significant only during the recovery period. These results indicate that ChE activity, as well as hematological parameters, may be useful as a diagnostic test for molinate exposure in aquatic organisms.