Bruggeman I M, Temmink J H, van Bladeren P J
Toxicol Appl Pharmacol. 1986 Apr;83(2):349-59. doi: 10.1016/0041-008x(86)90312-1.
Ally isothiocyanate has been reported to be a bladder carcinogen in male rats. On the other hand, benzyl isothiocyanate is an anti-carcinogen. These contradicting properties led us to investigate the cytotoxicity of these compounds in RL-4 rat hepatocytes. Since conjugation with glutathione plays an important role in the metabolism of these isothiocyanates, the glutathione and L-cysteine derivatives were also tested for cytotoxicity (electron microscopy, trypan blue exclusion, cell attachment, and inhibition of cell division). Both types of conjugates caused considerable toxicity: allyl isothiocyanate conjugates gave effects comparable to the parent compound, but benzyl isothiocyanate was more toxic than its conjugates. Addition of excess glutathione (greater than 4mM) to the free isothiocyanates as well as their conjugates abolished cytotoxicity up to the highest concentration tested (250 microM). Addition of excess L-cysteine (5 to 20 mM) lowered the effects but did not abolish them. The reaction of thiols with isothiocyanates was readily reversible: 15 min after dissolving the conjugates in buffer, pH 7.4, an equilibrium was established in which 9 to 15% of the conjugates was converted to free isothiocyanate. Two hours after addition of 1 mM of the L-cysteine conjugates to medium containing 5 mM glutathione, 80% of the total conjugates was present as the glutathione derivatives. The glutathione conjugates were similarly converted to L-cysteine conjugates. Glutathione conjugates are not able to enter the cell, thus their toxicity is presumably due to the release of free isothiocyanate, and in the presence of excess glutathione no toxicity was observed. L-cysteine derivatives are able to cross the cell membrane, thus excess L-cysteine diminishes cytotoxicity, since less free isothiocyanate is present outside the cells, but does not completely protect the cells. Glutathione and cysteine can be regarded as transporting agents for the isothiocyanates through the body. Initial detoxification can be followed by release of the reactive compound at some other site.
烯丙基异硫氰酸酯据报道是雄性大鼠的膀胱致癌物。另一方面，苄基异硫氰酸酯是一种抗癌剂。这些相互矛盾的特性促使我们研究这些化合物对RL - 4大鼠肝细胞的细胞毒性。由于与谷胱甘肽的结合在这些异硫氰酸酯的代谢中起重要作用，因此还测试了谷胱甘肽和L - 半胱氨酸衍生物的细胞毒性（电子显微镜、台盼蓝排斥、细胞附着和细胞分裂抑制）。两种类型的共轭物都引起了相当大的毒性：烯丙基异硫氰酸酯共轭物的效果与母体化合物相当，但苄基异硫氰酸酯比其共轭物毒性更大。向游离异硫氰酸酯及其共轭物中加入过量的谷胱甘肽（大于4mM），直至测试的最高浓度（250 microM）都消除了细胞毒性。加入过量的L - 半胱氨酸（5至20 mM）降低了效果，但并未消除。硫醇与异硫氰酸酯的反应很容易逆转：将共轭物溶解在pH 7.4的缓冲液中15分钟后，建立了一种平衡，其中9%至15%的共轭物转化为游离异硫氰酸酯。在含有5 mM谷胱甘肽的培养基中加入1 mM的L - 半胱氨酸共轭物两小时后，总共轭物的80%以谷胱甘肽衍生物的形式存在。谷胱甘肽共轭物同样转化为L - 半胱氨酸共轭物。谷胱甘肽共轭物无法进入细胞，因此其毒性可能是由于游离异硫氰酸酯的释放，并且在存在过量谷胱甘肽的情况下未观察到毒性。L - 半胱氨酸衍生物能够穿过细胞膜，因此过量的L - 半胱氨酸降低了细胞毒性，因为细胞外存在的游离异硫氰酸酯较少，但并不能完全保护细胞。谷胱甘肽和半胱氨酸可被视为异硫氰酸酯在体内的转运剂。初始解毒之后，反应性化合物可能会在其他部位释放。
