宠物小老鼠有毒吗?
有!而且非常危险,毒性巨大,可毒死一头牛,这就是臭名昭著的、对人类和动物有害的一类毒素——河豚毒素! 河豚毒素(tetrodotoxin)也叫TTX,是由海里的一种水母,叫河豚所产生的一种碱性蛋白质性毒素,目前发现的河豚毒素蛋白至少有12种以上[1],不同类型的河豚所产生的河豚毒素具有不同的生理活性,同一类型河豚产生的河豚毒素其生物活性几乎相同;反之,不同类型河豚所产生的氢氮酸根阳离子在细胞内的生化反应途径也是大同小异的,如图1A所示。可以根据细胞内生化反应的不同来区分不同的河豚毒素,也可以根据细胞对河豚毒素耐受程度的差异来划分不同类型的河豚[2][3] 图1. A. Cysteine proteinases (proteins that break down proteins) are present in low concentrations in the cytoplasm and are responsible for removing amino acids from the free amino acid pool as well as cleaving short peptides into smaller fragments. Thiol proteases belong to this group of cysteine proteinases; they contain a cys-x-pro sequence where x can be any amino acid except proline. The active site of the enzyme contains two cysteine residues, one of which is required for catalysis while the other one is essential for metal binding. B. Phospholipids are important structural components of cell membranes but their role in signaling pathways remains poorly understood. TTX affects voltage gated Na+ channels by increasing the permeability of phospholipid bilayer to Na+ ions thereby leading to inhibition of neuronal membrane depolarization and subsequent loss of neurotransmitter release. 人们最早发现河豚毒素是在1895年,当时法国巴黎一家医院的医生为一位患者做心脏手术时,发现患者的血清可以抑制电刺激引起的蛙肌肉收缩,后来经过进一步研究发现这种血清具有神经毒素的特性,从河豚身上提取到一种溶血素,称之为“torpedo poison”,简写成TTX。 在20世纪初,美国的科研人员用河豚毒素麻醉了猪、狗等实验动物,并证明了它对人体的作用效果[4]。