The in vivo mieronueleus assay was conducted by exposuring Chinese rare minnow (Gobiocypris rarus) in potassium dichromate solution followed by collecting the peripheral erythrocytes of the fish. The frequency of micronucleus increased with the variation of Cr(VI) potassium dichromate concentration and the exposure time. Results indicated that the fish had low backgroud MN frequencies in peripheral erythrocytes which could be significantly increased by hexavalent chromium, and there were obviously dose-response and time-response relationships between Cr(VI) and MN frequencies under certain conditions. Besides, observing 15000 cells per fish can effectively reduce test bias to ensure the reliability of the results. Generally, as compared to the negative control group, there was a significant increase in the MN frequencies of Chinese rare minnow for the groups in concentrations equal or greater than O.Olmg per liter. What is more, the MN frequencies in Chinese rare minnow* s peripheral erythrocytes were increased proportionally to the rise in concentrations, while a current of increase firstly and then decrease could be observed with the prolongation of exposed time, and it spent nearly 24h for the MN frequencies reaching the peak value in the higher concentrations of potassium dichromate solution. Furthermore, Chinese rare minnow seems to be more sensitive than other fishes. The present study supports the suitability and sensitivity of MNT in peripheral erythrocytes using Chinese rare minnow as an effective short-term in vivo assay system for monitoring aquatic environmental genotoxicants.%将稀有鮈鲫(Gobiocypris rarus)半静态暴露于重铬酸钾溶液中,研究发现稀有鮈鲫的本底微核率处于较低的水平,重铬酸钾在不同浓度和时间暴露后能明显观察到外周血红细胞微核增加.在一定条件下存在剂量-效应关系和时间-效应关系,表明稀有鮈鲫可用于鱼类外周血红细胞微核试验.试验中每尾鱼观察15000个细胞,能有效地减小试验偏差,保证试验结果的可靠性.暴露浓度大于等于0.01mg/L时,染毒组与空白组的外周血红细胞微核率有显著性差异,其微核率随染毒时间的延长呈先升高后下降的趋势,均在24h时出现所有测定时间微核率的峰值.与其他鱼类比较显示,稀有鮈鲫具有较高的敏感性,可用于遗传毒物诱发微核的监测.
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