State Key Laboratory of Microbial Technology, School of Life Sciences, Shandong University, 27 Shanda South Road, Jinan 250100, Shandong Province, PR China.
BMC Complement Altern Med. 2009 Nov 15;9:43. doi: 10.1186/1472-6882-9-43.
Semen armeniacae amarum (SAA) is a Chinese traditional medicine and has long been used to control acute lower respiratory tract infection and asthma, as a result of its expectorant and antiasthmatic activities. However, its mutagenicity in vitro and in vivo has not yet been reported. The Ames test for mutagenicity is used worldwide. The histidine contained in biological samples can induce histidine-deficient cells to replicate, which results in more his+ colonies than in negative control cells, therefore false-positive results may be obtained. So, it becomes a prerequisite to exclude the effects of any residual histidine from samples when they are assayed for their mutagenicity. Chinese traditional herbs, such as SAA, are histidine-containing biological sample, need modified Ames tests to assay their in vitro mutagenicity.
The mutagenicity of SAA was evaluated by the standard and two modified Ames tests. The first modification used the plate incorporation test same as standard Ames teat, but with new negative control systems, in which different amounts of histidine corresponding to different concentrations of SAA was incorporated. When the number of his+ revertants in SAA experiments was compared with that in new negative control, the effect of histidine contained in SAA could be eliminated. The second modification used a liquid suspension test similar to the standard Ames test, except with histidine-rich instead of histidine-limited medium. The aim of this change was to conceal the effect of histidine contained in SAA on the final counting of his+ revertants, and therefore to exclude false-positive results of SAA in the Ames test. Furthermore, the effect of SAA on chromosomal aberration in mammalian bone marrow cells was tested.
The standard Ames test showed a positive result for mutagenicity of SAA. In contrast, a negative response was obtained with the modified plate incorporation and modified suspension Ames tests. Moreover, no apparent chromosomal aberrations were observed in mammalian bone marrow cells treated with SAA.
The standard Ames test was not suitable for evaluating the mutagenicity of SAA, because false-positive result could be resulted by the histidine content in SAA. However, the two modified Ames tests were suitable, because the experimental results proved that the effect of histidine in SAA and therefore the false-positive result were effectively excluded in these two modified Ames tests. This conclusion needs more experimental data to support in the future. Moreover, the experimental results illustrated that SAA had no mutagenicity in vitro and in vivo. This was in agreement with the clinical safety of SAA long-term used in China.
苦杏仁是一种中国传统药物，长期以来一直被用于控制急性下呼吸道感染和哮喘，因为它具有祛痰和抗哮喘的作用。然而，其在体外和体内的致突变性尚未有报道。用于致突变性的艾姆斯试验在世界范围内被使用。生物样本中含有的组氨酸可诱导组氨酸缺陷型细胞进行复制，这导致出现比阴性对照细胞更多的 his+ 集落，因此可能会得到假阳性结果。因此，在检测其致突变性时，排除样品中任何残留组氨酸的影响成为一个前提条件。中国传统草药，如苦杏仁，是含有组氨酸的生物样本，需要经过改良的艾姆斯试验来检测其体外致突变性。
采用标准和两种改良艾姆斯试验评价苦杏仁的致突变性。第一种改良方法使用与标准艾姆斯试验相同的平板掺入试验，但采用了新的阴性对照系统，其中掺入了与苦杏仁不同浓度相对应的不同量的组氨酸。当比较苦杏仁实验中的 his+回复突变体数量与新阴性对照时，可以消除苦杏仁中所含组氨酸的影响。第二种改良方法使用类似于标准艾姆斯试验的液体悬浮试验，除了使用富含组氨酸的培养基而不是组氨酸有限的培养基。这样改变的目的是掩盖苦杏仁中所含组氨酸对最终计数 his+回复突变体的影响，从而排除艾姆斯试验中苦杏仁的假阳性结果。此外，还检测了苦杏仁对哺乳动物骨髓细胞染色体畸变的影响。
标准艾姆斯试验显示苦杏仁具有致突变性的阳性结果。相反，用改良的平板掺入和改良的悬浮艾姆斯试验得到了阴性反应。此外，用苦杏仁处理的哺乳动物骨髓细胞未观察到明显的染色体畸变。
标准艾姆斯试验不适合评价苦杏仁的致突变性，因为苦杏仁中的组氨酸含量可能导致假阳性结果。然而，两种改良的艾姆斯试验是合适的，因为实验结果证明，在这两种改良的艾姆斯试验中，有效地排除了苦杏仁中组氨酸的影响，从而排除了假阳性结果。这一结论需要更多的实验数据在未来加以支持。此外，实验结果表明，苦杏仁在体外和体内均无致突变性。这与苦杏仁在中国长期临床应用的安全性一致。
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