多代镉胁迫对家蝇幼虫血淋巴中镉和游离氨基酸的影响

Effects of multigenerational cadmium stress on cadmium and free amino acid in hemolymph of the Musca domestica larvae

目的了解镉胁迫对家蝇幼虫血淋巴镉浓度和游离氨基酸的影响。方法取1日龄家蝇幼虫,分别设对照(正常饲料饲养至第10代)组和镉胁迫1代(正常饲料饲养至第9代,第10代转饲含镉20 mg/kg饲料)组、镉胁迫10代(含镉20 mg/kg饲料饲养10代)组,每组(含300 g干麦麸)喂饲900头,每代染毒时间均为48 h。测量3日龄幼虫体重、体长及血淋巴镉离子浓度、游离氨基酸浓度。结果与对照组比较,镉胁迫1、10代家蝇3日龄幼虫体重、体长明显下降,血淋巴镉浓度显著升高,生糖氨基酸明显降低;镉胁迫10代组家蝇幼虫血淋巴的生酮氨基酸明显升高、丙氨酸明显降低、赖氨酸明显升高;镉胁迫1、10代组游离氨基酸总量无明显变化。与镉胁迫1代组比较,镉胁迫10代组家蝇3日龄幼虫体重、体长明显下降,血淋巴镉浓度显著升高,蛋氨酸、生糖氨基酸明显降低,生酮氨基酸升高。结论镉胁迫导致家蝇3日龄幼虫血淋巴中镉蓄积,游离氨基酸组成发生变化,抑制糖合成及生长发育。

Objective To explore the effects of cadmium stress lasted one generation and ten generations on cadmium concentration and free amino acid composition in hemolymph of the 3-day-instar Musca domestic larvae. Methods 1-day-instar Musca domestic larvae were divided into three groups： the control group （fed with normal diet from No.1 generation to No.10 generation）, the group exposed to cadmium only for one generation （fed with normal diet from No.1 generation to No.9 generation, No.10 generation fed with the artificial diets mixed with doses of Cd2＋ 20 mg/kg） and the group exposed to cadmium for 10 generations （fed with the artificial diets mixed with doses of Cd2＋ 20 mg/kg from No.1 generation to No. 10 generation）, larvae number in each group （fed with 300 g dry wheat bran） was 900, treatment time of every generation was 48 hours （from 1-dayinstar to 3-day-instar）. Weights and body length of the 3-day-instar larvae were measured,the concentration of cadmium and free amino acids were determined by atomic absorption spectrometry and automatic amino acid analyzer,respectively. Results Compared with the control group,weight and body length of the 3-day-instar Musca domestic larvae from the two cadmium stressed groups declined （P〈0.01）; The cadmium concentration in hemolymph of the 3-day-instar Musca domestic larvae from tow cadmium stressed groups increased （P〈0.01）; Total amount of the glucogenic amino acids in hemolymph from the two cadmium-stressed groups were lessened（P〈0.05 or P〈0.01 ）;Total amount of the ketogenic amino acids elevated（P〈0.05 or P〈 0.01 ） and alanine dropped （P〈0.01） and lysine rised （P〈0.01） in haemolymph of the 3-day-instar Musca domestic larvae from the group exposed to cadmium for 10 generations. Compared between two groups treated with cadmium ：weight and body length and methionine and total amount of the glucogenic amino acid in haemolymph of the 3-day-instar Musca domestic larvae exposed to cadmium for 10 generations were less and the cadmium concentration and ketone amino acids concentration in haemolymph was higher than those of the group exposed to cadmium for one generation （P〈0.05 or P〈0.01 ）. Conclusion The cadmium stress may lead to restrained growth and development, cadmium accumulation and changes of free amino acid composition in hemolymph of the 3-day-instar Musca domestic larvae, as well as inhibition of glucose synthesis. Key words： Cadmium stress; Musca domestica; Hemolymph; Accumulation; Free amino acid composition