2-乙酰基-4-四羟基-丁基咪唑对成年雌性大鼠的免疫毒性研究

Immunotoxicity of 2-acetyl-4-tetrahydroxybutyl imidazole on adult female rats

目的:探究Ⅲ类焦糖色制作过程中的主要副产物2-乙酰基-4-四羟基-丁基咪唑(THI)对雌性大鼠免疫系统的影响。方法:选取50只健康成年的SPF级雌性SD大鼠,随机分为5组,每组10只,进行THI经口灌胃染毒,剂量分别为0、0.1、0.5、2.5和5mg/kg,连续染毒30 d。记录大鼠体质量并测定胸腺和脾脏的脏器系数,取大鼠胸腺进行组织病理学观察,用全自动血细胞分析仪检测外周血中白细胞及各分类细胞的数量,通过淋巴细胞转化试验测定脾脏T淋巴细胞的增殖能力,用乳酸脱氢酶法测定脾脏NK细胞的活性,利用流式细胞术分析外周血、胸腺和脾脏中主要免疫细胞的比例变化。结果:THI染毒可使大鼠胸腺皮质/髓质面积比下降。与对照组相比,2.5和5 mg/kg的THI染毒能降低大鼠脾脏T淋巴细胞的增殖能力(P<0.01)。流式细胞术检测结果显示,与对照组相比,2.5 mg/kg及以上剂量THI染毒能降低大鼠外周血中白细胞总数和T淋巴细胞的比例(P<0.01),0.5 mg/kg及以上剂量组大鼠外周血中淋巴细胞数和B淋巴细胞的比例显著降低(P<0.05或P<0.01),5 mg/kg的THI染毒可使脾脏中T细胞的比例下降(P<0.01)、NK细胞的比例升高(P<0.01)。T细胞亚群的分析结果显示,5 mg/kg的THI能降低大鼠外周血中Th细胞的比例(P<0.01),0.5 mg/kg及以上剂量THI可使胸腺中Th细胞的比例升高(P<0.05或P<0.01)、CD4^(+)CD8^(+)双阳性T细胞的比例下降(P<0.05或P<0.01),2.5 mg/kg及以上剂量THI可升高胸腺中CTL细胞的比例(P<0.01)。结论:THI经口暴露可损伤雌性大鼠的免疫系统,外周血中淋巴细胞数目减少是其敏感的效应指标,本研究条件下THI免疫毒性的未观察到有害作用水平(NOAEL)为0.1 mg/kg。

OBJECTIVE:To investigate immunotoxicity of the main by-product 2-acetyl-4-tetrahydroxybutylimidazole(THI),in the process of classⅢcaramel color production,on female rats.METHODS:50 healthy adult female SD rats with SPF grade were randomly divided into 5 groups,10 rats in each group.They were given THI orally at doses of 0,0.1,0.5,2.5 and 5 mg/kg,respectively,continuously for 30 days.The followings were collected/evaluated:body weights,organ coefficients of thymus and spleen,histopathological evaluation of thymuses,number of white blood cells and various types of cells in peripheral blood,proliferation ability of spleen T lymphocytes,activities of NK cells,and flow cytometry evaluation of changes in the proportion of major immune cells in peripheral blood,thymus and spleen.RESULTS:THI exposure reduced the area ratio of thymus cortex/medulum and the proliferation ability of rat spleen T lymphocytes(with 2.5 and 5 mg/kg doses).The results of immunocytopathology showed that THI exposure at a dose of 2.5 mg/kg and above reduced the ratio of the total number of white blood cells and T lymphocytes in the peripheral blood and increase the ratio of NK cells in the spleen.The number of lymphocytes and the ratio of B lymphocytes in the peripheral blood were significantly reduced,and the ratio of T cells in the spleen was also reduced by the 5 mg/kg THI exposure.For the T cell subsets,5 mg/kg THI exposure reduced the ratio of Th cells in the peripheral blood.With doses of 0.5 mg/kg and above,THI increased the ratio of Th cells in the thymus and CD4^(+)CD8^(+)double positive.The proportions of non-positive T cells were reduced.With doses of 2.5 mg/kg and above,THI increased the proportion of CTL cells in the thymus.CONCLUSION:Oral exposure to THI caused damage to the immune system of female rats.In addition,changes in the number of lymphocytes in peripheral blood and the proportion of thymus T cell subsets were sensitive indicators.Thus,the no observed adverse effect level of THI immunotoxicity(NOAEL)is 0.1 mg/kg.