Changes in Carbohydrate Metabolism in Hemolymph and Fat Body of the Silkworm, Bombyx mori L., Exposed to Organophosphorus Insecticides

Effects of lethal and sublethal doses of widely used commercial-grade organophosphorus insecticides, namely fenitrothion and ethion, as a function of carbohydrate metabolism of hemolymph and fat body on Days 1, 3, 5, and 7 of the fifth-instar silkworm, Bombyx mori, were investigated. The results showed that pyruvate level and lactate dehydrogenase activity decreased with elevated lactate levels, indicating reduced mobilization of pyruvate into the Krebs cycle. Enzymes of Krebs cycle, namely succinate dehydrogenase and malate dehydrogenase, were significantly lowered, suggesting a decrease in respiration rate at the tissue level in silkworms due to toxicity induced by these organophosphorus insecticides. Further, the magnitude of these changes increased with time (Days 1 < 3 < 5 < 7). Therefore, it is apparent that both these insecticides may have induced toxicity on economically important silkworms by disturbing the carbohydrate metabolism. These results suggest that organophosphorus insecticides affect the carbohydrate metabolism in silkworms and consequently alter their metabolic functions to meet the required energy demands under the insecticidesʹ toxic stress conditions.