虫酰肼对甜菜夜蛾多巴脱羧酶和酪氨酸羟化酶的抑制作用

虫酰肼模拟昆虫蜕皮激素的作用干扰新表皮的形成。为了探讨虫酰肼对昆虫新表皮形成的影响是否与抑制表皮形成相关酶的活性有关， 本研究应用高效液相色谱-荧光检测法（HPLC-RP）， 测定了甜菜夜蛾Spodoptera exigua 5龄幼虫用虫酰肼处理不同时间（24， 48和72 h）后多巴脱羧酶和酪氨酸羟化酶的活性。结果表明： 用LC₁₁ （28.41 μmol/L）和LC₃₃ （85.23 μmol/L）两个亚致死剂量的虫酰肼处理5龄幼虫后， 多巴脱羧酶和酪氨酸羟化酶的活性均受到明显抑制， 高浓度的抑制作用大于低浓度的抑制作用。随着处理时间的延长， 同一剂量的抑制作用逐渐增强。进一步测定虫酰肼处理24， 48和72 h后5龄幼虫血淋巴、 脂肪体、 中肠、 表皮和头部的多巴脱羧酶和酪氨酸羟化酶的活性， 可看出虫酰肼对幼虫不同组织的多巴脱羧酶和酪氨酸羟化酶的活性也具有相似的抑制作用。结果提示， 虫酰肼对甜菜夜蛾幼虫多巴脱羧酶和酪氨酸羟化酶活性具有明显抑制作用， 幼虫新表皮形成受阻可能与虫酰肼抑制多巴脱羧酶和酪氨酸羟化酶的活性有关。

Inhibitory effects of tebufenozide on dopa decarboxylase and tyrosine hydroxylase in 5th instar larvae of Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae)

Tebufenozide acting in a similar fashion of ecdysone was found to produce phenotypic effects that finally interfere the formation of new larval cuticle in insects.To explore the effects of tebufenozide on the enzyme activities related to the formation of new cuticle in insects,high performance liquid chromatography(HPLC)-fluorescent assay was used to determine the activities of dopa decarboxylase(DDC) and tyrosine hydroxylase(TH) in 5th instar larvae of Spodoptera exigua which were continuously treated with tebufenozide for different time.The results indicated that after the larvae were treated with two sublethal concentrations(LC11 28.41 μmol/L and LC33 85.23 μmol/L) of tebufenozide,the activities of DDC and TH were significantly inhibited,and the inhibitory effect was more marked when the larvae were treated with tebufenozide at the high sublethal concentration than at the low sublethal concentration.The inhibition rates of DDC and TH activities were raised with treatment time at the same sublethal concentration.Tebufenozide had the similar inhibitory effects on DDC and TH activities in the midgut,head,fat body,hemolymph and cuticle of the 5th instar larvae as on those in the whole larval body.It is so concluded that the interference in the formation of new larval cuticle is likely related to the inhibition of DDC and TH activities by tebufenozide.