Cottrell S, Andrews C M, Clayton D, Powell C J
DH Department of Toxicology, St Bartholomew's Hospital Medical College, St Bartholomew's Centre for Research, London, UK.
Food Chem Toxicol. 1994 Jul;32(7):589-94. doi: 10.1016/0278-6915(94)90001-9.
Earlier studies have reported a reduction of vitamin K-dependent blood clotting factor activity and incidence of haemorrhagic death in rats fed butylated hydroxytoluene (BHT); however, the vitamin K status of the animals used in these studies was claimed to be inadequate. The aim of the study reported here was to determine the effect of BHT on vitamin K-dependent clotting factors in vitamin K-sufficient and vitamin K-supplemented rats. Rats given BHT (3000 mg/kg body weight) for up to 21 days, in a diet containing a minimum of 3 ppm vitamin K3 (six times the recommended requirement), showed decreased vitamin K-dependent blood clotting factor activities, demonstrated by increases in factor-specific clotting time assays. Clotting times were prolonged within 7 days, significantly increased within 14 days (P < 0.001) and maximally increased 5.5-fold at 21 days (P < 0.05). Supplementation with a further 250 ppm vitamin K3 reversed this effect. BHT did not increase prothrombin time (PT), the usual index of clotting. However, in a similar 14-day investigation, a small but significant increase in PT (up to 151%, P < 0.005) was seen within 7 days. Further vitamin K supplementation was incapable of reversing this effect completely. A similar trend was shown by activated partial thromboplastin time. The 1/51 dilution Thrombotest, a more sensitive indicator of vitamin K-dependent clotting factor activity in the rat, was significantly increased (more than four fold, P < 0.01) within 7 days. This increase was fully reversed by further vitamin K supplementation. Prolongation of Thrombotest time was significant at a BHT dose level of 600 mg/kg body weight per day and this could be reversed by further supplementation of only 3.0 ppm vitamin K. However, at dose levels of 125 mg BHT/kg body weight per day or less, no clotting defects were observed. These studies confirm that chronic administration of more than 600 mg BHT/kg/day to rats supplied with recommended amounts of vitamin K can depress clotting factors and precipitate haemorrhagic deaths. When further vitamin K is provided, these deaths could be prevented even though not all clotting abnormalities may be reversed. This study disapproves the proposal that BHT-related clotting factor defects are confined to rats of inadequate vitamin K status, but shows that such effects do not occur at dose levels lower than 600 mg/kg/day. The results further indicate that rats receiving a high dose of BHT have a higher vitamin K requirement than would otherwise be considered necessary. However, as BHT produces no clotting defects in these animals receiving an intake 1000 times the acceptable daily intake, such clotting effects are most unlikely to indicate a human safety problem for BHT.
早期研究报告称，给喂食丁基羟基甲苯（BHT）的大鼠补充维生素K后，其维生素K依赖性凝血因子活性降低，出血性死亡发生率降低；然而，这些研究中所使用动物的维生素K状态据说是不充足的。本文所报告研究的目的是确定BHT对维生素K充足和补充维生素K的大鼠体内维生素K依赖性凝血因子的影响。在含有至少3 ppm维生素K3（推荐需求量的六倍）的饮食中，给大鼠喂食BHT（3000 mg/kg体重）长达21天，结果显示维生素K依赖性凝血因子活性降低，这通过因子特异性凝血时间测定法的增加得以证明。凝血时间在7天内延长，14天内显著增加（P < 0.001），在21天时最大增加5.5倍（P < 0.05）。额外补充250 ppm维生素K3可逆转这种效应。BHT并未增加凝血酶原时间（PT），而PT是通常的凝血指标。然而，在一项类似的为期14天的研究中，在7天内观察到PT有小幅但显著的增加（高达151%，P < 0.005）。进一步补充维生素K无法完全逆转这种效应。活化部分凝血活酶时间也呈现出类似趋势。1/51稀释凝血试验，一种对大鼠体内维生素K依赖性凝血因子活性更敏感的指标，在7天内显著增加（超过四倍，P < 0.01）。这种增加通过进一步补充维生素K可完全逆转。当BHT剂量为每天600 mg/kg体重时，凝血试验时间延长显著，而仅额外补充3.0 ppm维生素K即可逆转这种情况。然而，当BHT剂量为每天125 mg/kg体重或更低时，未观察到凝血缺陷。这些研究证实，给摄入推荐量维生素K的大鼠长期施用超过600 mg BHT/kg/天可抑制凝血因子并引发出血性死亡。当提供更多维生素K时，即使并非所有凝血异常都能逆转，这些死亡也可预防。本研究不支持关于BHT相关凝血因子缺陷仅限于维生素K状态不足大鼠的提议，而是表明在低于600 mg/kg/天的剂量水平下不会出现这种效应。结果还进一步表明，接受高剂量BHT的大鼠比原本认为必要的情况有更高的维生素K需求。然而，由于BHT在这些摄入量为可接受每日摄入量1000倍的动物中未产生凝血缺陷，这种凝血效应极不可能表明BHT对人类存在安全问题。
