Twaddle Nathan C, Churchwell Mona I, McDaniel L Patrice, Doerge Daniel R
National Center for Toxicological Research, U S Food and Drug Administration, Jefferson, Arkansas 72079, USA.
J Agric Food Chem. 2004 Jun 30;52(13):4344-9. doi: 10.1021/jf0497657.
Acrylamide (AA) is a neurotoxic and carcinogenic contaminant that is formed during the cooking of starchy foods. Assessment of human risks from toxicants is routinely performed using laboratory rodents, and such testing requires careful control of unintended exposures, particularly through the diet. This study describes an analytical method based on liquid chromatography with electrospray tandem mass spectrometry that was used to measure endogenous AA in rodent diets and to survey a number of commercial products for contamination. Method sensitivity permitted accurate quantification of endogenous levels of AA in raw diets below 20 ppb. Autoclaving a standard rodent diet (NIH-31) increased the AA content 14-fold, from 17 to 240 ppb. A nutritionally equivalent diet that was sterilized by irradiation was found to contain approximately 10 ppb of AA (NIH-31IR). A toxicokinetic study of AA and its epoxide metabolite, glycidamide, was performed by switching mice from NIH-31IR to the autoclaved diet for a 30 min feeding period (average AA dose administered was 4.5 microg/kg of body weight). The concentrations of AA and glycidamide were measured in serum collected at various times. The elimination half-lives and the areas under the respective concentration-time curves were similar for AA and glycidamide. Mice maintained on autoclaved NIH-31 diet, but otherwise untreated, showed elevated steady state levels of a glycidamide-derived DNA adduct in liver relative to mice maintained on the irradiated diet. This study demonstrates that a heat sterilization procedure used in laboratory animal husbandry (i.e., autoclaving) can lead to the formation of significant levels of AA in basal diets used for toxicity testing. AA in rodent diets is bioavailable, is distributed to tissues, and is metabolically activated to a genotoxic metabolite, which produces quantifiable cumulative DNA damage. Although the contribution of endogenous AA to the incidence of tumors in multiple organs of rodents otherwise untreated in chronic carcinogenicity bioassays (i.e., control groups) is not known, the reduction of endogenous AA through the use of a suitable irradiated diet was deemed to be critical for ongoing studies of AA carcinogenicity and neurotoxicity.
丙烯酰胺（AA）是一种神经毒性和致癌性污染物，在淀粉类食物烹饪过程中形成。对有毒物质的人体风险评估通常使用实验啮齿动物进行，此类测试需要仔细控制意外暴露，尤其是通过饮食途径。本研究描述了一种基于液相色谱 - 电喷雾串联质谱的分析方法，该方法用于测量啮齿动物饮食中的内源性AA，并检测多种商业产品是否受到污染。方法的灵敏度允许准确量化生饲料中低于20 ppb的内源性AA水平。对标准啮齿动物饲料（NIH - 31）进行高压灭菌会使AA含量增加14倍，从17 ppb增至240 ppb。发现一种经辐照灭菌的营养等效饲料含有约10 ppb的AA（NIH - 31IR）。通过在30分钟的喂食期内将小鼠从NIH - 31IR饲料转换为高压灭菌饲料（平均给予的AA剂量为4.5微克/千克体重），对AA及其环氧化物代谢物缩水甘油酰胺进行了毒代动力学研究。在不同时间采集的血清中测量了AA和缩水甘油酰胺的浓度。AA和缩水甘油酰胺的消除半衰期以及各自浓度 - 时间曲线下的面积相似。相对于食用辐照饲料的小鼠，食用高压灭菌NIH - 31饲料但未进行其他处理的小鼠肝脏中，缩水甘油酰胺衍生的DNA加合物的稳态水平升高。本研究表明，实验动物饲养中使用的热灭菌程序（即高压灭菌）可导致用于毒性测试的基础饲料中形成大量的AA。啮齿动物饲料中的AA具有生物可利用性，可以分布到组织中，并被代谢激活为具有遗传毒性的代谢物，从而产生可量化的累积DNA损伤。尽管在慢性致癌性生物测定中（即对照组），内源性AA对未进行其他处理的啮齿动物多个器官肿瘤发生率的贡献尚不清楚，但通过使用合适的辐照饲料降低内源性AA被认为对正在进行的AA致癌性和神经毒性研究至关重要。
