5龄期和吐丝期家蚕丝腺中的抗坏血酸含量及抗氧化作用变化

Content and Antioxidant Effect Variation of Ascorbic Acid in Bombyx mori Silk Gland During the Fifth Instar and the Spinning Stage

抗坏血酸(AsA)是家蚕生长发育的必需维生素之一,具有抗氧化的生理功能。用分光光度法测定5龄期至吐丝期家蚕丝腺中的抗坏血酸含量、脱氢抗坏血酸(DHA)含量、抗坏血酸氧化酶(AAO)活性、抗坏血酸过氧化物酶(APX)活性和脱氢抗坏血酸还原酶(DHAR)活性,分析丝蛋白合成和分泌期间丝腺中抗坏血酸的抗氧化作用变化。结果显示在此期间丝腺中的AsA含量、总抗坏血酸(AsA和DHA)含量和AsA/DHA比值持续下降,DHA含量变化不显著,而没有检测到AAO和APX的活性,并且DHAR的活性在5龄期变化不显著,但在吐丝期持续下降。检测结果表明,伴随着丝蛋白的合成和分泌,家蚕丝腺中的抗坏血酸含量及抗氧化作用显著下降。

Ascorbic acid （AsA） is one of the essential vitamins for growth and development of the silkworm, Bombyx mori, which plays an important role in antioxidation. To investigate the variation of antioxidant effect of AsA in silk gland during synthesis and secretion of the silk protein, AsA content, dehydroascorbate （DHA） content, AsA oxidase （AAQ） activity, AsA peroxidase （APX） activity and DHA reductase （DHAR） activity in the silk gland were determined during the fifth instar and the spinning stage using spectrophotometric method. The results showed that, during these two periods, AsA content, total AsA （AsA＋DHA） content and AsA/DHA ratio continuously decreased, DHA content exhibited no sig- nificant variation, AAO and APX activity could not be detected in the silk gland, whereas DHAR activity slightly varied during the fifth instar but continuously decreased during the spinning stage. These results indicate that the content and antioxidant effect of AsA significantly decreases in the silk gland as the synthesis and secretion of silk protein advances.