Nickel accumulated in midugt of Spodoptera litura Fabricius could induce the expression of metal-lothionein,one of the most important detoxification proteins in organisms.In the present study,the effects of dietary nickel on the activities of detoxification enzymes,such as carboxylesterase(CarE) and glutathione S-transferase(GST) in the midgut of S.litura larvae have been studied to get an un-derstanding of the detoxification mechanisms of S.litura larvae to excessive nickel.Results showed that CarE activities in the midgut of the 5th instar larvae decreased at lower levels of nickel(≤5 mg/kg),while increased with increasing nickel doses at higher levels of nickel(≥10 mg/kg) exposure in suc-cessive 3 generations.CarE activities of the 6th instar larvae were also characterized as inhibited at low levels of nickel exposure,and improved at higher levels in the 1st generation.CarE activities of 6th instar larvae in the 2nd and 3rd generations were all lower than that in control.However,GST activities in the midgut of the 5th and 6th instar larvae all increased with increasing nickel doses(1―20 mg/kg) in diets.
SUN HongXia ZHOU Qiang TANG WenCheng SHU YingHua ZHANG GuRen
Effects of dietary nickel on apoptosis of hemocytes of the 6th instar larvae of Spodoptera litura Fabricius were evaluated using flow cytometry and Laser Scanning Confocal Microscopy (LSCM) by feeding S. litura larvae with artificial diets amended with different concentrations of nickel (1, 5, 10, 20 and 40 mg/kg) for 3 generations. Results showed that the hemocyte apoptosis rate of the 1st generation larvae increased with the increasing nickel concentrations in diet, and the apoptosis rate in the treatment with 40 mg/kg nickel was significantly higher than that in other treatments. In the 2nd generation, the highest hemocytes apoptosis rate was recorded in the treatment of the larvae exposed to 5 mg/kg nickel. The apoptosis rates in the larvae stressed by higher concentrations of nickel were lower than that in control. The apoptosis rates in the larvae exposed to nickel for 3 generations showed similar concentration-responses with that in the 2nd generation. However, the apoptosis rates in the larvae stressed with higher levels of nickel were all significantly inhibited in comparison with that in control. Therefore, effects of nickel stress on apoptosis of S. litura larvae were related with the nickel concentration in diets and the larval generations that were stressed by nickel.
SUN HongXiaXia QiangTANG WenChengZHOU QiangZHANG GuRenDANG Zhi
