代谢
硒在动物模型中的抗癌活性已经得到了很好的证实。迄今为止,涉及到的硒的活性形式尚未被确定,但是通过氢硒化物(H2Se)将硒转化为甲基化形式,如二甲基硒和三甲基硒离子是一个重要的代谢途径。通过控制硒进入这一途径各个点的入口,选择适当的起始化合物,可以更精确地确定硒的哪种形式对其抗癌活性负责。氯化形式的硒代甜菜碱[(CH3)2Se+CH2COOH]及其甲酯在大鼠体内被广泛代谢为单甲、二甲和三甲基硒化物,在很大程度上绕过了无机H2Se的中间池。使用二甲基苯并(a)蒽诱导的大鼠乳腺癌模型,在整个实验期间通过饮食补充1和2 ppm的硒来确定这些硒代甜菜碱的化学预防效果。这两种化合物都显示出剂量依赖性的抑制反应,并且它们似乎比亚硒酸盐略为有效。这些剂量对动物没有任何不良反应。硒代甜菜碱与砒霜(5 ppm砷)共同给药增强了硒代甜菜碱的肿瘤抑制效果,尽管砷本身完全无效。已知砒霜可以抑制硒甲基化过程中的某些步骤。甲基化硒化物具有显著的预防效果,砒霜的增强作用表明,部分甲基化的硒形式可能直接参与了硒的抗癌作用。
The anticarcinogenic activity of selenium in animal models is well established. The active forms of selenium involved have not been identified to date, but conversion of selenium via hydrogen selenide (H2Se) to methylated forms such as dimethylselenide and trimethylselenonium ion is an important metabolic fate. By controlling the entry of selenium into various points within this pathway through selection of appropriate starting compounds, it is possible to pinpoint more closely the form(s) of selenium responsible for its anticarcinogenic activity. Selenobetaine in the chloride form [(CH3)2Se+CH2COOH] and its methyl ester are extensively metabolized in the rat to mono-, di-, and trimethylated selenides, largely bypassing the inorganic H2Se intermediary pool. The chemopreventive efficacy of these selenobetaines was determined at 1 and 2 ppm selenium supplemented in the diet throughout the duration of the experiment using the dimethylbenz(a)anthracene induced mammary tumor model in rats. There was a dose-dependent inhibitory response to both compounds, and they appeared to be slightly more active than selenite. These doses were without any adverse effects on the animals. Coadministration of selenobetaine with arsenite (5 ppm arsenic) enhanced the tumor-suppressive effect of selenobetaine, although arsenic by itself was totally inactive. Arsenite is known to inhibit certain steps in selenium methylation. The substantial prophylactic efficacy of methylated selenides and the enhancement by arsenite suggest that partially methylated forms of selenium may be directly involved in the anticarcinogenic action of selenium.
来源:Hazardous Substances Data Bank (HSDB)