S.K. Parveen, K. Veeraiah, G. Vani and M. Vijaya Kumar
Abstract
The fish Catla catla fingerlings were exposed to the test toxicant an insecticide Flubendiamide for 24, 48, 72 and 96 hrs and the LC50 values were calculated and were reported to be 3.566, 3.456, 3.0221 and 2.892 mg5˹ respectively for 24, 48, 72 and 96 hrs. After determination of LC50 values the fish were exposed to sub-lethal concentration (1/10 th of 96 hrs. LC50 value i.e., 0.289 mg5â¹) for 24, 48, 72, 96 hrs and 8 days in the Indian major carp Catla catla was studied. Fingerlings were exposed to sub-lethal (0.289 mg5-¹) and lethal (2.892 mg5â¹) concentrations of flubendiamide for 24 hrs, 48 hrs, 96 hrs and only to the sub-lethal concentration exposed for 8 days. The role of AChE in cholinergic transmission is to regulate nervous transmission by reducing the concentration of acetylcholine (ACh) in the junction through AChE-catalyzed hydrolysis of ACh (Kopecka et al., 2004). AChE was identified as the enzyme responsible for termination of cholinergic transmission by cleavage of AChE to acetate and choline; AChE is found in cholinergic synapses in the brain as well as in autonomic ganglia, the neuromuscular junction, and the target tissues of the parasympathetic system (Silman and Sussman, 2005). The AChE activity is necessary to maintain normal behaviour and muscular function and represents a prime target called esteric site on which some toxicants can exert a detrimental effect by binding to it. Inhibition of the AChE activity results in a build-up process of acetylcholine causing prolonged excitatory postsynaptic potential. This results in repeated, uncontrolled firing of neurons leading to hyper stimulation of the nerve/muscle fibres, which leads paralysis, and eventual death. In the event of decreased ATPase system, phosphorylation may be preceded by activated phosphates to catalyse the liberation of inorganic phosphates from phosphate esters. Acetyl cholinesterase (AChE) activity is a frequently used parameter in environmental monitoring, usually in areas contaminated with pesticides, heavy metals and effluents. It is an enzyme that catalyses three hydrolysis of acetylcholine to choline and acetate in synaptic cleft. The aim of this study was to verify the relationship between the lethal and sub lethal concentration flubendiamide and the activity levels of Acetylcholinesterase (AChE).