氟化物对不同抗性家蚕品种的GST和AChE酶活性影响及雌雄个体间的酶活性差异

为了探明家蚕的耐氟性机制以及耐氟性在不同性别蚕体间的差异,以家蚕耐氟品种T6和氟化物敏感品种734为材料,自5龄起蚕开始分雌雄喂食清水和200 mg/kg NaF溶液浸泡后的桑叶,检测幼虫中肠谷胱甘肽-S-转移酶(GST)和头部乙酰胆碱酯酶(AChE)的活性变化。添食氟化物后耐氟和敏感家蚕品种5龄幼虫中肠的GST活力随添氟时间的变化趋势与对照组比较一致,且与对照组相比酶活性均呈增高趋势;敏感品种734添氟组5龄雌蚕的GST平均活力为雄蚕的1.486倍,耐氟品种T6添氟组5龄雌蚕的GST平均活力为雄蚕的1.529倍。敏感品种734对照组5龄幼虫在试验第3天头部的AChE酶活性显著升高,但添氟组雄蚕在试验第2天AChE酶活性即显著升高,而雌蚕的AChE酶活性在整个5龄试验期均呈平缓下降趋势;耐氟品种T6添氟组5龄雌、雄幼虫的AChE活力与对照组差异不大,酶活力随添氟时间的变化趋势也与对照组较为一致,均在第3天出现最低值;2个品种添氟组AChE酶活性的性别差异与GST相反,即雄蚕的AChE平均活力大于雌蚕。推测氟化物处理后耐氟家蚕品种仍然能够保持AChE酶活性水平,从而呈现对氟化物的耐受性;2种类型解毒酶活力在雌雄家蚕间的差异可能暗示同一品种雄蚕的耐氟能力较多涉及靶标抗性,而雌蚕的耐氟能力较多依赖于代谢抗性。

Effects of Fluoride on GST and AChE Activity in Bombyx mori Varieties with Different Resistance and Enzymatic Activity Difference Between Female and Male Larvae

To explore the mechanism of Bombyx mori resistance to fluoride and the difference of resistance between male and female Bombyx mori larvae,the fluoride resistant silkworm variety T6 and the fluoride sensitive variety 734 were used as materials.Their 5th instar newly exuviated larvae of both sexes were fed with mulberry leaves which had been soaked in clean water and 200 mg/kg NaF solution and were examined for activity variations of glutathione-S-transferase(GST) in midgut and acetylcholinesterase(AChE) in head of the larvae.The trend of GST activity variation in midgut of the 5th instar larvae of the two silkworm varieties after fluoride treatment was consistent with that of the clean water control group as the treatment time elongated,showing an increasing tendency compared with the control group.Average activity of GST in midgut of the 5th instar female larvae of the sensitive silkworm variety 734 in fluoride-treated group was 1.486 times to that of the male larvae.Average activity of GST in midgut of the 5th instar female larvae of the fluoride resistant silkworm variety T6 in fluoride-treated group was 1.529 times to that of the male larvae.In control group of the sensitive silkworm variety 734,AChE activity in head of the 5th instar larvae significantly increased at day 3 after treatment.But in fluoride treatment group of the sensitive silkworm variety 734,AChE activity in head of the male larvae significantly increased at day 2 after fluoride treatment,while that of the female larvae showed a mild decline trend in the whole trial period.The AChE activity and activity variation trend of the 5th instar female and male larvae of the fluoride resistant variety T6 in fluoride-treated group were similar to those of the control group,both of which reached their lowest values at day 3.The difference of AChE activity between male and female larvae of the two silkworm varieties was opposite to that of GST.That is,the average activity of AChE in male larvae was higher than that of female ones.It was assumed that AChE activity could be maintained in the fluoride resistant silkworm variety T6 after fluoride treatment,thus conferring this variety with fluoride tolerance.The activity difference of these two types of detoxification enzyme between female and male silkworm larvae suggests that the fluoride resistance capability of male silkworm is more related to target site resistance while that of female silkworm is more dependent on metabolic resistance.