Lok E, Mehta R, Jee P, Laver G, Nera E A, McMullen E, Clayson D B
Toxicology Research Division, Health Protection Branch, Health Canada, Ottawa, Ontario.
Carcinogenesis. 1995 May;16(5):1071-8. doi: 10.1093/carcin/16.5.1071.
Butylated hydroxytoluene (BHT) is a synthetic, food-use, phenolic antioxidant. It has previously been demonstrated to be operationally non-genotoxic and, in addition, failed to induce biologically significant increases in cellular proliferation in the liver, urinary bladder and thyroid gland on feeding to young adult Wistar rats. Nevertheless, it has been reported to enhance the yield of liver tumors when fed to rats or mice that developed an appreciable background incidence of these tumors without treatment. In order to resolve this situation, cell proliferation in response to BHT treatment was studied in enzyme-altered foci (EAF) induced in male Fischer 344 rats using the Solt-Farber procedure. It was demonstrated that feeding 0.5% dietary BHT for 30 days after the induction of EAF led to a 20- to 30-fold increase in the gamma-glutamyltranspeptidase-positive areas in both DEN- and saline-initiated rat livers, but to no major effects in glutathione S-transferase placental form (GSTP)-positive foci. Cell proliferation rates within EAF and surrounding normal liver were measured using different histological techniques. Nuclear labeling with [3H]thymidine and proliferating cell nuclear antigen (PCNA) over the total hepatocyte population indicated that BHT approximately doubled nuclear labeling in rats initiated with DEN. PCNA labeling in GSTP-positive foci was not affected by BHT. In GSTP-positive foci, evaluation of nucleolar organizer regions (AgNOR), which reflect cell proliferative in addition to transcriptional activity of ribosomal RNA, was achieved using a novel double staining technique. BHT diet did not affect the number of AgNOR per nucleus or the percentage AgNOR area/nucleus. Nevertheless, both PCNA labeling and the AgNOR area per nucleus were significantly greater in GSTP-positive foci compared with non-focal regions in rats fed either BHT or control diets. These results are discussed in the light of further experimental work required to determine the relevance of these data to possible human risk assessment for BHT.
丁基羟基甲苯（BHT）是一种合成的、用于食品的酚类抗氧化剂。此前已证明其在操作上无遗传毒性，此外，给年轻成年Wistar大鼠喂食后，它不会在肝脏、膀胱和甲状腺中诱导细胞增殖出现生物学上显著的增加。然而，据报道，给那些在未经处理时就有相当高背景肿瘤发生率的大鼠或小鼠喂食BHT时，会提高肝脏肿瘤的发生率。为了解决这种情况，使用Solt-Farber方法，在雄性Fischer 344大鼠诱导的酶改变灶（EAF）中研究了对BHT处理的细胞增殖反应。结果表明，在EAF诱导后喂食0.5%的膳食BHT 30天，导致二乙基亚硝胺（DEN）启动和盐水启动的大鼠肝脏中γ-谷氨酰转肽酶阳性区域增加20至30倍，但对谷胱甘肽S-转移酶胎盘型（GSTP）阳性灶没有重大影响。使用不同的组织学技术测量了EAF和周围正常肝脏内的细胞增殖率。用[3H]胸腺嘧啶核苷和增殖细胞核抗原（PCNA）对整个肝细胞群体进行核标记表明，BHT使DEN启动的大鼠的核标记增加了约一倍。GSTP阳性灶中的PCNA标记不受BHT影响。在GSTP阳性灶中，使用一种新型双重染色技术评估核仁组织区（AgNOR），其除了反映核糖体RNA的转录活性外还反映细胞增殖。BHT饮食不影响每个细胞核的AgNOR数量或AgNOR面积/细胞核的百分比。然而，与喂食BHT或对照饮食的大鼠的非灶性区域相比，GSTP阳性灶中的PCNA标记和每个细胞核的AgNOR面积均显著更大。根据确定这些数据与BHT可能的人类风险评估的相关性所需的进一步实验工作，对这些结果进行了讨论。
