Cd^2＋急性胁迫下方格星虫体腔液消化酶活力和游离氨基酸的变化

CHANGES OF DIGESTIVE ENZYME ACTIVITIES AND FREE AMINO ACIDS IN SIPUNCULUS NUDUS COELOMIC FLUID UNDER ACUTE STRESS OF CD^(2+)

为了解Cd^(2+)急性胁迫下方格星虫体腔液消化酶活力和游离氨基酸的变化规律,采用毒理学试验方法,在确定Cd^(2+)对方格星虫毒性强度的基础上,选取48h最低致死浓度为试验浓度,研究该浓度Cd^(2+)胁迫下方格星虫体腔液消化酶活力和游离氨基酸的动态变化。结果表明:方格星虫死亡率随着Cd^(2+)浓度的升高而增加,Cd^(2+)对方格星虫的24h和48h的LC50分别为37.80和22.68 mg/L。在48h最小致死浓度下,Cd^(2+)对方格星虫体腔液蛋白酶和淀粉酶活力在试验周期内均表现为抑制,且淀粉酶活力受到的抑制作用较强;Cd^(2+)胁迫前期脂肪酶活力显著升高(P<0.05),24h后又显著降低(P<0.05),48h时仅为初始水平的40%,说明低浓度Cd^(2+)对脂肪酶活力有诱导作用,高浓度Cd^(2+)则产生抑制。方格星虫体腔液游离氨基酸的组成和含量在Cd^(2+)胁迫48h内均有显著变化(P<0.05)。各游离氨基酸含量及氨基酸总量在24h前均无显著变化(P>0.05),24h后先上升后下降(P<0.05),36h的游离氨基酸总量达到初始水平的2倍以上,为145.50 mg/100 m L,大部分游离氨基酸组成百分比也在24h前较稳定,24h后呈现峰值变化。总之,Cd^(2+)急性胁迫对方格星虫体腔液消化酶活力和游离氨基酸均有显著影响(P<0.05),且消化酶活力与游离氨基酸含量和组成的变化与胁迫时间有关。

The current study investigated the acute toxicity of Cd2＋ to Sipunculus nudus Linnaeus using toxicological methods. To do this, the peanutworms were exposed to Cd2＋ stress for 48h at minimum lethal concentration, and the dynamic changes of digestive enzyme activities and free amino acids in their coelomic fluid were analyzed. The results showed that the mortality of peanutworms increased with the increasing Cd2＋ concentration. The LC50 of Cd2＋ after 24h and 48h were 37.80 mg/L and 22.68 mg/L, respectively. Cd2＋ exposure had inhibitory effects on protease and amylase activities in coelomic fluid during the whole experimental period. The lipase activity increased （P〈0.05） at the early time of the exposure, but inhibited significantly （P〈0.05） after 24h. The content and composition of free amino acids in coelomic fluid of peanutworms had significant changes during the 48 hours. Each free amino acid and the total amino acid had no significant changes （P〉0.05） at the first 24 hours, and then the contents of that increased significantly （P〈0.05） and decreased significantly later at the next 24 hours （P〈0.05）. The total amino acid reached 145.50 mg/ 100 mL at 36h, twice as initial level. The free amino acids composition had a similar regulation pattern with total amino acid. No significant change was observed at first 24h and then reached peak level after that. The results suggest that acute stress of Cd2＋ significantly impact digestive enzyme activities and free amino acids in Sipunculus nudus coelomic fluid with a time-dependent pattern.