The effect of recombinant growth hormone (GH)on insulin-like growth factor-Ⅰ (IGF-Ⅰ) expression in mud carp, Cirrhinus molitorella
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摘要:
使用半定量RT-PCR方法,研究了鲮(Cirrhinus molitorella)各组织中IGF-ⅠmRNA组织表达,并分析重组鲮GH处理后鲮IGF-Ⅰ表达变化情况。结果表明,鲮IGF-ⅠmRNA在肝组织中表达最高,其次是肾和脑,另外在肠、鳃、脾、性腺和心脏组织中也有表达,而在肌肉、皮肤中没有检测到鲮IGF-ⅠmRNA的表达;按120 μg·g-1鱼体重的剂量经腹腔注射重组鲮GH,观察12 h后鲮IGF-Ⅰ表达变化情况,发现经重组鲮GH处理后,鲮肝组织IGF-ⅠmRNA表达水平显著升高,脑组织IGF-ⅠmRNA表达水平也稍有升高,而在肌肉中仍未检测到IGF-ⅠmRNA的表达;重组鲮GH处理前后,对照组中鲮血清中IGF-Ⅰ的含量为145.59±21.84 ng·mL-1,试验组中鲮血清中IGF-Ⅰ的含量为247.71±2.83 ng·mL-1,经t检验,P=0.043 < 0.05,表明重组鲮GH处理前后鲮血清中IGF-Ⅰ的含量存在显著性差异。
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关键词:
- 鲮 /
- 胰岛素样生长因子-Ⅰ /
- 生长激素
Abstract:Expression patterns of IGF-ⅠmRNA in different tissues of mud carp (Cirrhinus molitorella)were studied using semi-quantitative RT-PCR method and the effects of recombinant mud carp growth hormone(rmcGH)on expression of IGF-Ⅰin mud carp were investigated. The IGF-ⅠmRNA was detected successfully in liver, kidney, brain, intestine, gill, spleen, gonad, and heart, and no IGF-ⅠmRNA was detected in skin and muscle. The IGF-Ⅰ mRNA detected was higher in liver than in other tissues. Mud carp were received either intra-peritoneal injections of rmcGH (120 μg·g-1 body weight) or vehicle, tissue samples and blood were collected 12 hour later. Total RNA was isolated and assayed for IGF-ⅠmRNA using semi-quantitative RT-PCR. Blood was extracted to determine the levels of IGF-Ⅰ in serum. IGF-Ⅰlevels increased from 145.59±21.84 to 247.71±2.83 ng·mL-1 (P=0.043) in the serum after rmcGH injection.
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Keywords:
- mud carp /
- Cirrhinus molitorella /
- insulin-like growth factor-Ⅰ /
- growth hormone
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雪卡毒素是一种可引起人类中毒的珊瑚鱼毒素,毒性极强。近年来,由于海上捕捞及潜水猎鱼日益增多,有将近400种珊瑚鱼成了水产食谱和高档酒楼的海鲜美食,使原本多发生于渔船上的热带亚热带珊瑚鱼雪卡中毒事件转而发生于家庭或海鲜餐厅,造成对消费者健康的威胁。带有雪卡毒素的鱼类主要存在于太平洋、印度洋、大西洋等热带、亚热带海域。集中分布在南纬至北纬35°之间最常见含有雪卡毒素的鱼类,以聚居于珊瑚礁一带觅食的海鱼为主,主要有老虎斑、金钱龙趸、蓝瓜子斑、老鼠斑、苏眉、西星斑、豹星斑、燕尾星斑、杉斑及东星斑[1]。虽然因食用含雪卡毒素的珊瑚鱼而中毒的事件时常发生,然而很少有人知道雪卡毒素是一种什么物质,对它的分子结构和化学性质更是不了解。因此,本文不仅对雪卡毒素作一简单介绍,而且对它的研究进展也作一综述,这将为减少和防止雪卡中毒事件的发生具有重要的意义。
1. 雪卡毒素结构和化学性质
雪卡毒素(ciguatoxin,CTX),又称西加毒素,分子内包含13个相连的环醚,醚环的大小包括有5、6、7、8、9元环,整个骨架具有反式或顺式的立体化学特征。化学结构式如下:
雪卡毒素是一种无色、耐热、非结晶体,能溶于极性有机溶剂如甲醇、乙醇、丙酮,但不溶于苯和水,也不易被胃酸破坏[2],是一种脂溶性的有机化合物。雪卡毒素属神经毒素,按毒素毒性程度可分为4个等级:猛毒,如食入有毒鱼肉200 g即能致死;强毒,产生严重的运动神经麻痹,不可起立;轻毒,产生轻度知觉麻痹或运动麻痹;微毒,症状极轻或不显毒性。雪卡毒素对灵长类动物的半致死量为2.0 μg · kg-1[3]。
2. 雪卡毒素的药理作用与提取及合成
雪卡毒素主要存在于鱼肉、内脏、尤其是生殖腺的鱼卵中。雪卡毒素具有抑制钙离子作用,低浓度有强烈的和不可逆的胆碱酶抑制作用,能增强肌肉和神经细胞中钠离子通透性,使细胞膜去极化而引发神经系统的中毒症状。此外,由于雪卡毒素对脑外伤造成的昏迷有很好的疗效,对癌症等也有一定的抑制作用,所以雪卡毒素在国际市场上有贵黄金之称,其售价1.785亿美元· kg-1。为了获得纯的雪卡毒素,一方面采用从鱼中提取的方法。日本从1909年开始,花费49年才从珊瑚鱼的卵巢中提取分离出雪卡毒素,又用了近10年才完成其工业提取的研究。由于从珊瑚鱼提取雪卡毒素的工艺复杂,而且珊瑚鱼资源提取的量也少,世界上仅有少数国家能完成这项研究。1982年我国大连海洋渔业公司医师王维国先生,用他多年研究海洋药物的经验,独辟蹊径,带领有关人员仅用2年时间,在我国首次从河豚鱼肝脏中提取雪卡毒素,又用2年时间完成其工业提取的研究并转入商业性生产阶段,成为我国独家批量生产雪卡毒素的单位,并进入国际市场[4]。另一方面,用化学合成的方法可以获得雪卡毒素,化学合成雪卡毒素的研究工作主要集中在日本。据报道,日本科学家已能精确合成雪卡毒素的碳架结构,并将合成的雪卡毒素碳架结构用于雪卡毒素免疫分析抗体制备的人工抗原研究[5-7]。
3. 雪卡毒素的中毒症状及中毒现状
雪卡毒素主要来自于涡鞭藻——冈比尔盘藻(Cambierdisc toxicus),是该藻产生的毒素。冈比尔盘藻通常生活在珊瑚礁周围,也附着在其它海藻上生长,在太平洋、大西洋中广泛分布。其它微藻如P.lima、Ostreopsis siamensis和O.ovata等也能产生雪卡毒素[1]。通过食物链,由小鱼吃冈比尔盘藻或附着冈比尔盘藻的海藻,大鱼吃小鱼层层积聚并累积。雪卡毒素不会被高温分解,故烹煮过程并不能除去毒素。雪卡毒素中毒有临界值,毒素进入血液后,需要很长时间才能将毒素排出,患者日后若再次接触到雪卡毒素,就算吃下很少的份量,超过临界值时也会产生中毒症状。中毒症状表现为在进食含雪卡毒素的珊瑚鱼数小时后,会出现肠胃或神经系统不适等现象,主要病征包括呕吐、腹泻、口角及四肢麻痹、冷热感觉颠倒、关节及肌肉疼痛等,病症可维持数天至数星期不等。
据报道全世界每年至少2万人不同程度的遭受雪卡毒素的伤害[8-9]。在香港,1997年发生16宗食用珊瑚鱼雪卡中毒的案例,103人中毒;1998年1月发生70多人被怀疑吃了在珊瑚礁附近觅食的含有珊瑚鱼毒素的深海大鱼而中毒;1999年3~5月爆发因食用“杉斑”等珊瑚鱼雪卡中毒的案例27宗,118人中毒[10]。特别是近年,因食用珊瑚鱼导致的雪卡中毒事件更是频繁发生,据香港卫生署统计2004年香港累计雪卡中毒人数超过255人,为2003年雪卡中毒27人的9倍(人民网香港2005年1月27日电,http://news.163.com/05/0127/11/1B3MBF860001124U.html)。雪卡中毒事件在沿海城市如上海、青岛、北海、广州、湛江、汕头和深圳多次发生,尤其自2004年以来,发生雪卡中毒事件更多,累计仅在广东雪卡中毒的人数已超过200人,如2004年11月中山市小榄镇发生一起婚宴80多人因食用珊瑚鱼而致雪卡中毒[羊城晚报,2004-11-24(A2)],因此,雪卡中毒被评为2004年广东食品安全八大事件之一。2005年,雪卡中毒事件仍然时有发生,在广州、大连、深圳等地常有因食用珊瑚鱼而中毒的事件报道。2005年“十一”黄金周期间,香港报道了10人吃鱼中毒[新明日报,2005-10-6(A)]。截止到2005年10月,香港雪卡中毒的事件累计达到40余起[11]。为此,世界卫生组织和海洋渔业工作组多次召开会议商讨雪卡中毒的预防措施和分析方法,并鼓励发展雪卡毒素的现场快速检测方法。
4. 雪卡毒素的检测分析现状
现有对雪卡毒素的仪器分析如气相色谱、液相色谱和质谱等方法[12-14],由于对于样品的前处理操作繁琐,不适应现场简单快速和大批量样品残留检测的要求。有学者采用生物标志物和细胞活性测定间接反应雪卡毒素的含量[15-16],但测试过程时间长,灵敏度低,未广泛使用。另有学者通过制备雪卡毒素的多克隆和单克隆抗体,采用免疫方法测定雪卡毒素,但测试过程需要多次温育和洗涤,使用致癌性的邻苯二胺作为显色底物,步骤繁琐,也不适于现场测定[17-19]。目前,国内外对雪卡毒素的测定主要采用美国Oceanit Test Systems, Inc.(www.cigua.com)公司研制的免疫膜测定试剂盒[15],国内多家单位和项目申请者购买该试剂盒进行雪卡毒素分析,测试1个样本需要成本100多元。可见,对雪卡毒素的分析尚缺乏快速准确并适应现场的检测方法。
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图 3 半定量RT-PCR检测重组鲮GH处理前后鲮actin和IGF-ⅠmRNA的组织表达
B1. 半定量RT-PCR检测对照组中鲮各组织中actin mRNA的表达;B2. 半定量RT-PCR检测对照组中鲮各组织中IGF-ⅠmRNA的表达;C1. 半定量RT-PCR检测处理组中鲮各组织中actin mRNA的表达;C2. 半定量RT-PCR检测处理组中鲮各组织中IGF-ⅠmRNA的表达;D. 处理前后鲮组织IGF-ⅠmRNA的相对表达;M. 100 bp DNA分子量标准;NC. 负对照;1~10. 肝、脑、肌肉、肾、肠、鳃、脾、性腺、心脏、皮肤
Figure 3. Semi-quantitative RT-PCR analysis of expression of Actin and IGF-Ⅰ mRNA in various tissues in mud carp
B1. Actin mRNA was detected in various tissues by semi-quantitative RT-PCR in control group; B2. IGF-ⅠmRNA was detected in various tissues by semi-quantitative RT-PCR in control group; C1. Actin mRNA was detected in various tissues by semi-quantitative RT-PCR in rmcGH in treated group; C2. IGF-Ⅰ mRNA was detected in various tissues by semi-quantitative RT-PCR in rmcGH in treated group; D. relative quantity of IGF-ⅠmRNA in various tissues in mud carp; M.100 bp DNA molecular weight marker; NC. a negative control (no template); 1~10. brain, liver, muscle, kidney, intestine, gill, spleen, gonad, heart, skin
表 1 扩增IGF-Ⅰ、Actin的引物序列
Table 1 Oligonucleotide primers used to amplify cDNA for mud carp IGF-Ⅰand Actin
引物 primer 序列 sequence Actin-F 5′-GTGTTGGCG/ATACAGGTCCTTACG-3′ Actin-R 5′-CAGACTACCTC/GATGAAGATCCTGAC-3′ IGF-Ⅰ-F 5′-ATGGAAAACCAGCGCCTCTTC-3′ IGF-Ⅰ-R 5′-TGCATGTCCTTCTTGAAGCAAG-3′ 表 2 对照组和重组鲮IGF-Ⅰ处理组鲮血清中GH和IGF-Ⅰ浓度
Table 2 The GH and IGF-Ⅰconcentration in sera in control and rmc IGF-Ⅰtreated fish
浓度±S.E.(n=3)/ng·mL-1 concentration±S.E. 对照组
control重组鲮IGF-Ⅰ处理组
rmcIGF-Ⅰtreated groupP值 胰岛素样生长因子-Ⅰ浓度
IGF-Ⅰconcentration145.59±21.84 247.71±2.83 P=0.043<0.05 生长激素浓度
GH concentration0.037±0.0067 0.053±0.0067 P=0.508>0.05 -
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