The relationship between hemorrhage induced by butylated hydroxytoluene and its antioxidant properties or structural characteristics

2 Final Report on the Safety Assessment of Butylated Hydroxyanisole

Butylated hydroxyanisole (BHA) is used in cosmetic formulations as a chemical preservative and as an antioxidant. Both animal and human studies have shown that BHA is absorbed from the gastrointestinal tract and metabolized. Tissue storage may occur with BHA because of its lipid solubility. However, the amount stored is limited by rapid metabolism and excretion. Reported acute oral LD50 values for BHA in rats varied from 2.0 to > 5.0 g/kg. Formulations containing BHA elicited, at most, minimal or moderate skin and eye irritation in rabbits. An extensive number of subchronic and chronic oral studies have been conducted and are reviewed.

BHA given orally or parenterally to mice and rats was shown to inhibit the carcinogenic effects of a broad range of chemical carcinogens. BHA has been shown to inhibit mutagenesis and was not a mutagenic agent in standard in vitro tests. No evidence of carcinogenicity was observed when BHA was administered to mice by subcutaneous injection, by intraperitoneal injection, or by topical application. No carcinogenesis was demonstrated following dietary administration of BHA to either rats or dogs. An increased incidence of forestomach papillomas and squamous cell carcinomas has been observed in rats fed BHA. Studies with pregnant rabbits, mice, rats, and hamsters receiving BHA during gestation by a variety of oral dosage regimens revealed no significant embryotoxic or teratogenic effects.

Clinical data for BHA in cosmetic formulations indicated that they were generally nonsensitizing, nonphotosensitizing, and only minimally or mildly irritating. It is concluded that BHA is safe as a cosmetic ingredient in the present practices of use.

Final report on the safety assessment of BHT(1)

BHT is the recognized name in the cosmetics industry for butylated hydroxytoluene. BHT is used in a wide range of cosmetic formulations as an antioxidant at concentrations from 0.0002% to 0.5%. BHT does penetrate the skin, but the relatively low amount absorbed remains primarily in the skin. Oral studies demonstrate that BHT is metabolized. The major metabolites appear as the carboxylic acid of BHT and its glucuronide in urine. At acute doses of 0.5 to 1.0 g/kg, some renal and hepatic damage was seen in male rats. Short-term repeated exposure to comparable doses produced hepatic toxic effects in male and female rats. Subchronic feeding and intraperitoneal studies in rats with BHT at lower doses produced increased liver weight, and decreased activity of several hepatic enzymes. In addition to liver and kidney effects, BHT applied to the skin was associated with toxic effects in lung tissue. BHT was not a reproductive or developmental toxin in animals. BHT has been found to enhance and to inhibit the humoral immune response in animals. BHT itself was not generally considered genotoxic, although it did modify the genotoxicity of other agents. BHT has been associated with hepatocellular and pulmonary adenomas in animals, but was not considered carcinogenic and actually was associated with a decreased incidence of neoplasms. BHT has been shown to have tumor promotion effects, to be anticarcinogenic, and to have no effect on other carcinogenic agents, depending on the target organ, exposure parameters, the carcinogen, and the animal tested. Various mechanism studies suggested that BHT toxicity is related to an electrophillic metabolite. In a predictive clinical test, 100% BHT was a mild irritant and a moderate sensitizer. In provocative skin tests, BHT (in the 1% to 2% concentration range) produced positive reactions in a small number of patients. Clinical testing did not find any depigmentation associated with dermal exposure to BHT, although a few case reports of depigmentation were found. The Cosmetic Ingredient Review Expert Panel recognized that oral exposure to BHT was associated with toxic effects in some studies and was negative in others. BHT applied to the skin, however, appears to remain in the skin or pass through only slowly and does not produce systemic exposures to BHT or its metabolites seen with oral exposures. Although there were only limited studies that evaluated the effect of BHT on the skin, the available studies, along with the case literature, demonstrate no significant irritation, sensitization, or photosensitization. Recognizing the low concentration at which this ingredient is currently used in cosmetic formulations, it was concluded that BHT is safe as used in cosmetic formulations.

Comparison of the effect of low- and high-dose dietary butylated hydroxytoluene on microsome-mediated aflatoxin B1-DNA binding

Butylated hydroxytoluene (BHT) is known to inhibit tumor formation due to several chemical carcinogens including aflatoxin B1 (AFB1). Pre-treatment of laboratory animals with high doses of BHT (0.75% for 15 days in diet) is associated with pathological effects. The mechanism of action of BHT against AFB1 carcinogenesis is by induction of liver glutathione (GSH) S-transferases. As a result, the formation of AFB1-DNA binding is effectively inhibited. In the present study, effects of low and high doses of dietary BHT on in vitro activation and inactivation of AFB1 was examined. BHT feeding to rats at a dose of 0.75% for 15 days caused a significant increase in the GSH S-transferase activity. Addition of liver cytosolic fractions prepared from the rats pre-treated with high dose BHT to the cell free system caused a 48% inhibition in AFB1-DNA binding. In contrast, low dose BHT feeding (0.06% for 6 months) had little influence on GSH S-transferase activity. This was corroborated when addition of liver cytosol from low dose BHT-treated rats failed to inhibit microsome-mediated AFB1-DNA binding as compared to that of control. It is concluded that the permitted dose of BHT, added to processed food as preservative, plays no role in the biotransformation of AFB1.

Haemorrhagic toxicity of a large dose of alpha-, beta-, gamma- and delta-tocopherols, ubiquinone, beta-carotene, retinol acetate and L-ascorbic acid in the rat

Antioxidants occasionally have become prooxidants when a large amount was ingested. The haemorrhagic toxicity of butylated hydroxytoluene, a synthetic antioxidant, may involve such a mechanism. This study investigated whether haemorrhage is induced by overdoses of tocopherols, beta-carotene, ubiquinone or L-ascorbic acid, which are representative biological antioxidants. Male Jcl:SD rats (six rats/group) were fed d-alpha, d-beta, d-gamma or d-delta-tocopherols, ubiquinone Q-10, beta-carotene or retinol acetate at a level of 0.5%, or L-ascorbic acid at 5% in the diet for 7 days. Only two rats given retinol acetate died with lung haemorrhages. Haemorrhages were observed in five or six, six, one, one, one or one of six surviving rats given d-alpha, d-beta or d-gamma-tocopherols, ubiquinone Q-10, beta-carotene or retinol acetate, respectively (except for a retinol group in which four rats survived). Major haemorrhages were noted in the epididymis. In the alpha-, beta- and gamma-tocopherol, ubiquinone Q-10, beta-carotene or retinol acetate-treated groups, prothrombin and kaoline-activated partial thromboplastin time indices were 26-28, 37, 59, 42, 63 and 65% or 27-28, 35, 65, 38, 59 and 28%, respectively, of the control values. Only the prothrombin index was significantly decreased to 67% in delta-tocopherol-administered rates, whereas controls and those receiving L-ascorbic acid showed no signs of bleeding or coagulation defect. The same tendency was also seen in the decreasing effect on vitamin K-dependent blood coagulation factors. These results suggest that the four naturally occurring tocopherols have a tendency to cause haemorrhage in the order of alpha > beta > gamma > delta, and ubiquinone Q-10 and beta-carotene als0o have relatively strong and weak haemorrhagic effects, respectively, with regard to prothrombin and partial thromboplastin time indices.

Retinoid-induced hemorrhaging and bone toxicity in rats fed diets deficient in vitamin K

The recent increase in the clinical use of synthetic vitamin A compounds has led to concern of possible side effects. Some of these effects are known to be influenced by dietary levels of vitamin K. We therefore compared the toxic effects of 13-cis-retinoic acid (13cisRA), retinyl acetate (ROAc), and N-(4-hydroxyphenyl)retinamide (4HPR) in male Sprague-Dawley rats maintained on diets containing different levels of vitamin K. Animals were fed either an NIH-07 diet supplemented with menadione (3.1 ppm vitamin K3), an NIH-07 diet not supplemented with menadione, or an AIN-076 purified diet devoid of vitamin K. The retinoids had no effect on prothrombin times of animals fed the supplemented diet. When menadione was omitted from the diet, however, 4HPR-dosed animals had elevated prothrombin times. This effect was observed as early as Day 7 and was accompanied by one confirmed hemorrhagic death. 13cisRA-dosed animals showed no change in prothrombin times. In the high-dose ROAc group, there was a twofold increase in prothrombin times but only after prolonged dosing. In animals fed the NIH-07 diets, 13cisRA and ROAc induced multiple bone fractures at all dose levels. In contrast, 4HPR administered at the highest dose induced only one fracture in one animal. Animals fed the purified diet lost weight faster and diet sooner than those maintained on the other diets. Bone fractures were not observed in these animals because of early deaths resulting from hemorrhaging. For all retinoid-dosed groups maintained on the purified diet, changes in prothrombin times occured as early as 1 week. The order of effect was 4HPR greater than ROAc greater than 13cisRA, with increases in prothrombin times correlating with increases in hemorrhagic deaths. Hence, the degree of retinoid-induced hemorrhage, but not the incidence of bone fractures, was inversely related to vitamin K levels in the diet. 13cisRA and ROAc, but not 4HPR, caused a dose-dependent reduction in plasma osteocalcin, an effect that correlated with retinoid-induced bone effects. In contrast, serum alkaline phosphatase was elevated in animals dosed with 13cisRA or 4HPR but not in those dose with ROAc. For this enzyme, the electrophoretic pattern on agarose gel showed a decrease, compared to controls, in the major isozyme in serum of ROAc-dosed animals. Hence, plasma osteocalcin is a better predictor of retinoid-induced bone effects than serum alkaline phosphatase.

Decrease in blood coagulation factors II (prothrombin), VII, IX and X in the rat after a single oral dose of butylated hydroxytoluene

Male Sprague-Dawley rats were given butylated hydroxytoluene (BHT) in a dose of 800 mg/kg body weight orally, and 0.5-72 hr later plasma concentrations of factors II, VII, IX and X and hepatic levels of BHT and BHT quinone methide (2,6-di-tert-butyl-4-methylene-2,5-cyclohexadienone) were determined. Levels of factors II, VII, X and IX were reduced 36-60 hr after BHT treatment, but by 72 hr, those most affected (VII and IX) showed some recovery and X had returned to normal. Hepatic levels of BHT reached a maximum 3 hr (a major peak) and 24 hr after BHT dosing and BHT quinone methide reached a maximum at 6 and 24 hr (a major peak). In rats given BHT orally in doses of 200, 400 and 800 mg/kg, factors II, VII and X decreased after 48 hr only in rats given the highest dosage, but factor IX was more susceptible to BHT and showed a dose-dependent decrease. Phylloquinone (1 mg/rat) injected ip 24 hr after the administration of 800 mg BHT/kg maintained normal levels of factors VII and X and an almost normal level of factor IX, but had little effect on the level of factor II. In studies of the effects of drug-metabolizing-enzyme modifiers, neither ip pretreatment with 75 mg phenobarbital sodium/kg for 3 days nor the feeding of 1% cysteine in the diet throughout the experiment prevented the decrease in vitamin-K-dependent factors by 800 mg BHT/kg, but 2-day ip pretreatment with 60 mg cobaltous chloride/kg/day maintained normal levels of factors II and VII and reduced the BHT effect on factors IX and X. SKF 525A (50 mg/kg) injected ip either 30 min before or 12 hr after BHT treatment partially prevented the decrease in factors II, VII and X, or in all four factors, respectively. Thus the decrease in vitamin K-dependent factors may be the same with a single oral dose of BHT as with dietary BHT, and the anticoagulant effect may require the metabolic activation of BHT.

Feeding of butylated hydroxytoluene to rats caused a rapid decrease in blood coagulation factors II (prothrombin), VII, IX and X

Male Sprague-Dawley rats were fed a diet containing 1.2% butylated hydroxytoluene (BHT) for 1-7 days, and blood coagulation factors II, VII, VIII, IX and X, and platelet aggregation were measured. The plasma concentrations of factors II, VII, IX and X were significantly reduced in a time-dependent fashion when BHT was administered for 2-7 days and haemorrhages in epididymis were found in rats given BHT for 4-7 days. On the contrary, thrombin-induced and calcium-required aggregation of washed platelets was unchanged throughout the experiment. These results suggest that factors II, VII, IX and X rapidly decrease immediately after the administration of BHT, but hypoaggregability of washed platelets reported previously may be a secondary defect caused by bleeding.

Lung hemorrhagic toxicity of butylated hydroxyanisole in the rat

Male Sprague-Dawley rats were injected intraperitoneally (i.p.) with butylated hydroxyanisole (BHA) at doses of 0, 1, 4, 16, 64, 256, 384, 576, 864, 1296 and 1944 mg/kg/day for 7 days. Deaths occurred in a dose- and time-dependent manner when BHA was given in amounts greater than 576 mg/kg. The LD50 was 881 (484-1440) mg/kg. Intracranial hemorrhage was found in the dead rats, and lung hemorrhage was observed in the survivors given BHA at doses greater than 384 mg/kg/day. Histopathologically, intra-alveolar hemorrhages, thickening of alveoli and deposition of lipids in the lungs were observed. The prothrombin index was decreased only in rats given BHA at a level of 384 mg/kg/day. These observations suggest that BHA and/or its metabolite cause pulmonary hemorrhagic damage in rats. The mechanism of hemorrhage may be different from that of bleeding induced by butylated hydroxytoluene.

Differences in the haemorrhagic toxicity of aspirin between rats and mice

Rats and mice were fed a diet containing aspirin at levels of 0, 0.3, 0.6 and 1.2% for 1 and 4 weeks. Haemorrhagic death and/or haemorrhagic anaemia occurred in rats in a dose-dependent manner. Prothrombin and kaolin-activated partial thromboplastin time indices were also decreased depending on the daily doses. However, no conspicuous haemorrhagic signs were found in mice given aspirin. These results suggest marked differences in haemorrhagic effects of aspirin between rats and mice. From results of supplementary experiments with two metabolites of aspirin, salicylic acid and gentisic acid, and from the fact of close relationship between hepatic concentration of salicylic acid and haemorrhagic effects of aspirin, it is inferred that salicylic acid may be a precursor for the active metabolite(s) to cause haemorrhage. The mechanism of species differences of aspirin is discussed.

Intestinal absorption of nutrients in animals dosed orally with retinoids: considerations for chemopreventive studies

Biochemical measurements demonstrate that, in some species, various retinoids administered in the diet, can reduce the tissue contents of several lipid-soluble compounds: vitamin K, alpha-tocopherol, cholesterol, and vitamin A itself. The effect is probably due to an interference with intestinal absorption, as indicated by use of radioactive compounds and administration of bile acids. In male rats, a vitamin K deficiency induced by retinoids in the diet can lead to fatal hemorrhaging. Although retinoids inhibit the uptake of dietary cholesterol, they do not change plasma and tissue concentrations of the endogenous compound. Conversely, cholesterol in the diet appears to interfere with the absorption of retinyl esters. alpha-Tocopherol deficiency caused by retinoids results in tissues with low antioxidant and high peroxide concentrations. Humans may be less susceptible to these effects of retinoids, which, however, still deserve consideration in the planning of clinical trials.

Toxicological assessment of the hemostatic system, regulatory requirements, and industry practice

Disturbances of the hemostatic system which may be caused by chemicals include hemorrhagic diathesis, caused by inhibition of blood clotting, impairment of platelet function, and hyperactivity of fibrinolysis. Activation of the plasmatic clotting system, platelet aggregation, and inhibition of fibrinolysis may lead to thromboembolic complications. Although much is known about the functions of the hemostatic system a rational and cost-effective approach for its assessment in industrial toxicology is lacking. In this review the physiology of hemostasis and the available laboratory tests are discussed, current regulatory requirements are described, and industry practice is analyzed based on experience accumulated over the last 23 years. Proposals for a more flexible and scientific approach to testing of hemostatic mechanisms in toxicology are made.

The lack of effect of tertiary butylhydroquinone on prothrombin time in male rats

The potential for tertiary butylhydroquinone (TBHQ) to produce hemorrhagic death similar to that seen after butylated hydroxytoluene (BHT) treatment was tested in male rats. Groups of male rats were given three consecutive daily doses of 380, 760 or 1520 mg/kg/day BHT or 50, 100 or 150 mg/kg TBHQ. Twenty-four hours following the last dose, the rats were killed, blood was taken for prothrombin determinations and gross autopsies were performed. No evidence of hemorrhage was found in any of the animals. BHT caused a significant dose-dependent increase in prothrombin times, while the prothrombin times of the TBHQ rats were comparable to the controls. Since hypoprothrombinemia plays a major role in producing hemorrhagic death, these data indicate that the potential for THBQ to have such an effect is low.

The role of 2,6-di-tert-butyl-4-methylene-2,5-cyclohexadienone (BHT quinone methide) in the metabolism of butylated hydroxytoluene

Male rats were fed 5.45 mmol/100 g diet butylated hydroxytoluene (BHT) or 2,6-di-tert-butyl-4-hydroxymethylphenol (BHT alcohol) in either a standard or purified diet for 1 wk, after which their livers were analysed for levels of unconjugated BHT metabolites and their blood clotting times were assayed. The BHT quinone methide, 2,6-di-tert-butyl-4-methylene-2,5-cyclohexadienone, was only found in appreciable concentrations (6-9 micrograms/g liver) in the livers of rats given BHT. For rats fed the purified diet, BHT and BHT alcohol caused significant reductions of the prothrombin index to 23 and 70%, respectively, of the control value, though rats fed the standard diet were not similarly affected. Liver concentrations of BHT in rats fed BHT alcohol also varied according to diet, indicating that the metabolic pathway may be affected by diet. Biliary excretion of the quinone methide was observed in rats given 140 mg BHT alcohol ip.

Metabolic studies in the rat with 2,4,6-tri-t-butylphenol: a haemorrhagic antioxidant structurally related to butylated hydroxytoluene

Single oral doses of the haemorrhagic antioxidant 2,4,6-tri-t-butylphenol (260 mg/kg) were well absorbed in the rat. Peak blood levels of this compound were reached in 15-60 min. The blood elimination half-lives were 18.2 min for the alpha-phase and 11.8 h for the slower beta-phase. Max. tissue concns. of this compound were reached 2-3 h in the liver, 2-6 h in kidneys, 1.5-2.5 h in spleen and greater than 24 h in epididymal adipose tissues. This compound and its metabolites were not excreted in the urine; a metabolite but not the parent compound was detected in the faeces. The faecal metabolite had a mol. wt. of 261, and was considered to be 2,4,6-tri-t-butylphenoxy radical. 2,4,6-Tri-t-butylphenoxy radical was also detected in the bile of rats after oral administration of the parent phenol.

Haemorrhagic toxicosis in rats given butylated hydroxytoluene

Vascular permeability, platelet function, blood coagulation and fibrinolytic activity were examined in Sprague-Dawley male rats given 1.20% butylated hydroxytoluene (BHT) in the diet for 1 week. BHT significantly increased the leakage of Evans blue from blood into epididymus. BHT inhibited the ADP-induced platelet aggregation and decreased the platelet factor 3 availability. Plasma prothrombin, factors IX, X, VII and VIII were decreased in rats given BHT. Fibrinolytic activity was little influenced by BHT-feeding.

Effects of four bisphenolic antioxidants on prothrombin levels of rat plasma

Male Sprague--Dawley rats were fed 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 4,4'-butylidenebis(3-methyl-6-tert-butylphenol) or 4,4'-methylenebis(2,6-di-tert-butylphenol) at a level of 1.135 mmol/100 g in the diet for 1 week. The prothrombin and kaolin-partially thromboplastin time (PTT) indices were significantly decreased to 32% and 37% of control values in rats given 2,2'-methylenebis(4-methyl-6-tert-butylphenol). A slight decrease in prothrombin index of rats given 4,4'-butylidenebis(3-methyl-6-tert-butylphenol) was also observed.

Effect of butylated hydroxytoluene on the lipid composition of rat liver

Hepatic lipids were studied in Sprague-Dawley male rats given butylated hydroxytoluene(BHT) at a level of 1.20% for 1 week. BHT significantly increased cholesteryl esters and phospholipids but decreased triglycerides, non-esterified fatty acids and diglycerides. BHT also increased phosphatidylethanolamine or decreased phosphatidylinositol and lysophosphatidylcholine. Fatty acid composition of each lipid class was also changed by BHT-feeding. The decrease in 16 : 1/16 : 0, 18 1/18 : 0 and 20 : 4/18 :2 ratios of total lipids, non-esterified fatty acids or phospholipids of BHT-given rats suggests that BHT decreases the activity of fatty acid desaturase in the liver.

Increase of NAD(P)H:quinone reductase by dietary antioxidants: possible role in protection against carcinogenesis and toxicity

2(3)-tert-Butyl-4-hydroxyanisole (BHA) is one of several widely used antioxidant food additives that protect against chemical carcinogenesis and toxicity. The present report concerns the enhancement of dicoumarol-inhibited NAD(P)H:quinone reductase [NAD(P)H dehydrogenase (quinone); NAD(P)H:(quinone acceptor) oxidoreductase, EC 1.6.99.2] activity in mouse tissues in response to dietary administration of BHA. Cytosolic quinone reductase specific activity was increased significantly in 10 of 15 tissues examined from BHA-fed mice. The greatest proportionate increase, to 10 times control levels, was observed in liver. BHA also increased the quinone reductase activities of kidney, lung, and the mucosa of the upper small intestine severalfold. The increases of quinone reductase activities in liver and digestive tissues in response to BHA were comparable to the increases previously observed in glutathione S-transferase (EC 2.5.1.18) and epoxide hydratase (EC 3.3.2.3) activities. Quinones are among the toxic products of oxidative metabolism of aromatic hydrocarbons. NAD(P)H:quinone reductase exhibits broad specificity for structurally diverse hydrophobic quinones and may facilitate the microsomal metabolism of quinones to readily excreted conjugates. The protective effects of BHA appear to be due, at least in part, to the ability of this antioxidant to increase the activities in rodent tissues of several enzymes involved in the nonoxidative metabolism of a wide variety of xenobiotics.

The acute toxicity of butylated hydroxytoluene and its metabolites in mice

the acute toxicity of butylated hydroxytoluene (BHT) and four of its metabolites, 2,6-di-tert-butyl-4-hydroperoxy-4-methyl-2,5-cyclohexadien-1-one (BHT-OOH), 2,6-di-tert-butyl-4-hydroxy-4-methyl-2,5-cyclohexadien-1-one (BHT-OH), 2,6-di-tert-butyl-p-benzoquinone (DBQ), and 2,6-di-tert-butyl-4-[(methylthio)methyl]phenol (BHT-SCH3) was studied in young male mice following intraperitonel administration. The i.p. LD50 values of BHT, BHT-OOH, BHT-OH, DBQ, and BHT-SCH3 wee 3550, 190, above 1600, 2270, and 1840 mg/kg, respectively. These results suggest that BHT-OOH probably is the most toxic metabolite of BHt.

4-tert-butyl-2,6-diisopropylphenol: Another phenol inducing hemorrhage in rats

Male Sprague-Dawley rats were fed with 3,5-di-tert-butylphenol, 2,4-di-tert-butylphenol, 4-tert-butyl-2,6-diisopropylphenol, 2-tert-butyl-4-sec-butylphenol or 2-,6-di-tert-butyl-4-methylphenol (BHT) at a level of 2.27 mmol% in the diet for 1 week. One rat given 4-tert-butyl-2,6diisopropylphenol died: post mortem examination revealed hematocoelia, intratesticular, intraepididymal and intramuscular hematoma. The other rats in this group suffered from severe hemorrhagic anemia; and the prothombin index was significantly decreased.