家蚕品种7532和大造在高温冲击下中肠抗氧化酶活性的变化

为了探讨家蚕抗高温冲击的生理机制,比较了高温(36℃)冲击对家蚕二化性品种7532和大造5龄幼虫死亡率和中肠抗氧化酶活性的影响。自5龄24h起,供试家蚕品种大造经高温冲击24h以后,幼虫的累计死亡率就显著升高;而7532经高温冲击48h以后,幼虫的累计死亡率才显著升高。高温冲击48～72h,7532的5龄幼虫中肠组织中超氧化物歧化酶(SOD)活性较高,且随高温冲击时间延长显著增加,而大造5龄幼虫中肠组织中SOD的活性较低,且高温冲击时间延长后的变化不显著;7532的5龄幼虫中肠组织中的过氧化氢酶(CAT)活性在高温冲击48h后显著升高,而大造5龄幼虫中肠组织中的CAT活性在高温冲击24h后显著下降,直到72h后才显著升高,并且7532中肠组织中的CAT活性显著高于在大造中肠组织中的活性;2个品种5龄幼虫中肠组织中的谷胱甘肽S-转移酶(GST)活性分别在高温冲击24h和48h时达到峰值,在高温冲击48～72h期间,7532中肠组织中的GST活性显著高于大造中肠组织中的活性。上述结果提示,家蚕品种7532抗高温冲击能力较家蚕品种大造强,与其中肠组织中的抗氧化酶活性升高有关。

Activity Variations of Antioxidant Enzymes in Midguts of Bombyx mori Strians 7532 and Dazao Under High Temperature Shock

In order to explore the physiological mechanism of Bombyx mori resistance to high temperature shock,effects of high temperature (36 ℃) shock on mortality rates and antioxidant enzymes in the midgut of the 5th instar larvae were compared between 7532 and Dazao,two bivoltine strains of Bombyx mori.Abrupt increase of larval cumulative mortality was observed in strain Dazao after 24 h of high temperature shock starting from 24 h of the 5th instar,while the same in-crease was observed in strain 7532 after 48 h of the shock.After high temperature shock for 48 to 72 h,superoxide dismutase (SOD) activity in midgut tissue of 7532 increased with the duration of shock treatment and maintained at a high level.However,SOD activity in midgut tissue of Dazao did not vary significantly when duration of shock treatment was increased and maintained at a relatively low level.After high temperature shock for 48 h,catalase (CAT) activity in midgut tissue of 7532 increased significantly,while that in Dazao decreased significantly till 72 h at which CAT activity turned to increase significantly.Nevertheless,CAT activity in the midgut tissue of 7532 was significantly higher than that in Dazao.Glutathione S-transferase ( GST) activity reached the peak value in midgut tissue of 7532 at 48 h and in strain Dazao at 24 h.Strain 7532 had significantly higher activity of GST from 48 h to 72 h of high temperature shock compared to Dazao.The obtained results showed that the increased antioxidant enzymatic activity in midgut tissue of 7532 was related to its stronger resistance against high temperature shock than strain Dazao.