5龄期和吐丝期家蚕丝腺中的过氧化氢代谢与谷胱甘肽氧化还原循环特征

Characteristic Analysis of Hydrogen Peroxide Metabolism and Glutathione Redox Cycle in Bombyx mori Silk Gland During the Fifth Instar and the Spinning Stage

机体内的氧化还原状态对细胞的生命活动有着重要影响,而过氧化氢(H2O2)代谢和谷胱甘肽氧化还原循环与之密切相关。利用分光光度法检测5龄期和吐丝期家蚕丝腺中参与H2O2代谢与谷胱甘肽氧化还原循环调控的各种因子(氧化剂、还原剂和抗氧化剂)的含量变化。在2个时期的丝腺中未能检测到谷胱甘肽过氧化物酶(GPX)和谷胱甘肽还原酶(GR)活性。5龄期丝腺中的H2O2含量显著升高,超氧化物歧化酶(SOD)活性、氧化型谷胱甘肽(GSSG)含量、还原型谷胱甘肽(GSH)/GSSG比值变化不显著,过氧化氢酶(CAT)活性、GSH含量、总谷胱甘肽含量、硫氧还蛋白过氧化物酶(TPX)活性和硫氧还蛋白还原酶(TrxR)活性显著下降。吐丝期丝腺中的H2O2含量、SOD活性、GSH含量、GSSG含量、总谷胱甘肽含量和TPX活性显著下降,CAT活性、GSH/GSSG比值和TrxR活性显著升高。检测结果表明,5龄期丝腺中的CAT活性和TPX活性下降是导致H2O2含量升高的原因,但是TPX活性和TrxR活性下降导致的GSH/GSSG比值变化并不显著;吐丝期丝腺中的SOD活性下降导致H2O2含量下降,TPX活性下降和TrxR活性升高导致GSH/GSSG比值升高。可见,家蚕丝腺中的H2O2代谢与谷胱甘肽氧化还原循环特征在5龄期和吐丝期存在显著差异。

Redox status in organisms is very important to cellular life activity, and is closely related to hydrogen peroxide （H2O2） metabolism and gtutathione redox cycle. The content variations of various factors （oxidizer, reducer and antioxi- dant） involving in the regulation of H2O2 metabolism and glutathione redox cycle in Bombyx mori silk gland during the fifth instar and the spinning stage were determined using spectrophotometric method. Activities of glutathione peroxidase （GPX） and glutathione reductase （GR） could not be detected in the silk gland during these two periods. In silk gland during the fifth instar, H2O2 content significantly increased, superoxide dismutase （SOD） activity, oxidized glutathione （GSSG） content and reduced glutathione （GSH）/GSSG ratio varied slightly, catalase （CAT） activity, GSH content, total glutathione content, thioredoxin peroxidase （TPX） activity and thioredoxin reductase （TrxR） activity significantly decreased. H202 content, SOD activity, GSH content, GSSG content, total glutathione content and TPX activity significantly decreased but CAT activity, GSH/ GSSG ratio and TrxR activity significantly increased in the silk gland during spinning stage. These results indicated that, the decline of CAT activity and TPX activity resulted in the increase of H2O2 content, and the decline of TPX activity and TrxR activity did not influence GSH/GSSG ratio obviously in the silk gland during the fifth instar. The decline of H2O2 content was resulted from the decline of SOD activity, and the in- crease of GSH/GSSG ratio was due to the decline of TPX activity and the increase of TrxR activity in silk gland during the spinning stage. It was shown that there were significant difference in H2O2 metabolism and glutathione redox cycle in silk gland between the fifth instar and the spinning stage.