Sublethal effects of an organophosphorus insecticide (RPR-II) on biochemical parameters of tilapia, Oreochromis mossambicus.

The effect of exposure to sublethal concentrations (0.017 mg L(-1), 1/10 of LC50) of the novel organophosphate (OP) insecticide, 2-butenoic acid-3-(diethoxyphosphinothioyl) methyl ester (RPR-II) on biochemical parameters in Oreochromis mossambicus was studied during exposure for 3, 7, 15, 30 and its recovery response after seven days. Acetylcholinesterase (AChE) activity of brain, gill and muscle was inhibited by 67%, 77% and 73% respectively on day-30. The plasma and kidney alanine aminotransferase (AlaAT), and aspartate aminotransferase (AspAT) activity increased, while decreases were observed in gill and liver. Increases in acid phosphatase (AcP), and alkaline phosphatase (AP) activities were observed in plasma, gill, and kidney, and reductions of 20% and 61% in liver AcP and AP, respectively. Depletion of glycogen was observed in all tissues, an indication of typical stress related response of the fish with pesticide. Lactate dehydrogenase (LDH) activity decreased in liver and muscle, indicating tissue damage but a significant increase in LDH activity in gill and brain was observed. Depletion of glutathione (GSH) was observed in all tissues, thereby enhancing lipid peroxidation resulting in cell damage. The induction in hepatic glutathione-S-transferase (GST) levels indicates protection against the toxicity of xenobiotic-induced lipid peroxidation. There was a significant recovery in the above biochemical parameters, in all tissues of fish after a recovery period of seven days. These results revealed that the OP insecticide RPR-II is highly toxic and affects the intermediary metabolism of O. mossambicus.