Assessment of Malate dehydgrogenase activity in different tissues of the commom carp Cyprinus carpio on exposure to acute lethal and chronic sublethal toxicity of Phorate

Phorate is an organophosphate insecticide (OPI) which is widely used throughout the world as a broad spectrum insecticide on numerous crops including paddy and groundnut. The impact of acute lethal and chronic sublethal (ALCS) toxicity of phorate was investigated on Malate dehydrogenase (MDH) activity in the vital organs of fish such as gill, liver, muscle, kidney and brain of the freshwater common carp Cyprinus carpio (C. carpio), an economically important edible fish, having great commercial value. Fish were exposed to acute lethal toxicity (LC50/96 hours 0.71 ppm/l) of Phorate (ALTP) for one day and 4 days and chronic sublethal toxicity (one-tenth of the LC50/96 hours 0.071 ppm/l) of Phorate (CSTP) for 1, 7, 15 and 30 days and the MDH activity was observed in the target organs after the completion stipulated exposure period. The activity of MDH was decreased significantly (P<0.05) at day 1 and day 4 in all the organs of the fish exposed to ALTP and that decrement was progressed from day 1 to day 4 whereas in the fish exposed to CSTP, from day 1 to day 7 there was increase in the decrement but from day 7 to day 30 it was regressed in all the organs of the fish significantly (P<0.05). The findings of this study have demonstrated the sensitivity of MDH activity in different tissues of C. carpio on exposure to lethal and sublethal concentrations of Phorate and organophosphates.