Toxic impact of ingested Jatropherol-I on selected enzymatic activities and the ultrastructure of midgut cells in silkworm, Bombyx mori L.

Abstract:  Jatropherol-I, a phorbol-type diterpene from Jatropha curcas seeds was found highly toxic to third instars silkworm larvae after ingestion with LC₅₀ values 0.5793, 0.2197 and 0.1578 mg/ml at 48, 72 and 120 h respectively. The acute toxicity was associated with changes in activities of several midgut enzymes and pathological changes in midgut epithelial cells. Jatropherol-I caused various fluctuations in activities of different midgut enzymes in third instars larvae of silkworm. Compared with controls, both esterase and carboxyliesterase showed significantly depressed activities at 3 h ( t -test, P < 0.05) and increased activities at 24 h and rapidly decreased activities at 48 h after ingestion of 0.125 and 0.25 mg/ml of Jatropherol-I. Jatropherol-I induced two (E4 and E5) and depressed one (E2) of midgut esterase isozymes analysed 3 h after ingestion. There was no significantly different glutathione S-transferase activity between most of treated silkworm and control ( t -test, P > 0.05). Activities of acetylcholinesterase fluctuated weakly in treated silkworm in 48 h. Jatropherol-I induced a gradual decline in midgut protease activities in silkworm with an obvious dose- and time-dependent effect. Jatropherol-I also caused pathological changes in midgut cells, especially in their endoplasmic reticulum. They were noted slight dilatation on 12 h exposure, while extreme dilatation, vesiculations and shedding of ribosome from membrane were observed in endoplasmic reticulum after a longer time exposure. Other pathological changes in microvilli, lysosome, mitochondria and chromatin were also observed in midgut cell of treated silkworm.