Experimental data from closed chamber gas uptake studies in rodents suggest lower uptake rate of chemical than calculated from literature values on alveolar ventilation

Experimental data obtained in vivo with the closed-chamber gas uptake technique have been reported for a series of volatile chemicals. Pharmacokinetic analyses of these data have been performed either by using a two-compartment model or physiological models. In the former the transfer rate of chemical from ambient air to body is defined by the clearance of uptake. In the latter models the transfer rate depends on alveolar ventilation, cardiac output, and blood: air partition coefficient. In this communication we describe the quantitative relationship between clearance of uptake and alveolar ventilation, cardiac output, and blood: air partition coefficient. Theoretical values of clearance of uptake were calculated for a variety of volatile chemicals using literature data on alveolar ventilation, cardiac output, and blood: air partition coefficient. For most chemicals the experimentally determined values in rats and mice were about 60% of the theoretical values. This suggests that the inhalatory uptake rate of chemical may be overestimated if literature values of alveolar ventilation are used in physiological pharmacokinetic models for rodents.     

Occupational chronic exposure to organic solvents

Summary Four female assistants using a mixture of xylenes and ethylbenzeneas solvent in a histology laboratory were examined according to the concentrations of solvents in blood and the excretion of phenolic compounds in urine during 24 h. The average concentrations of (m+p)-xylene and ethylbenzene in air were between 56 and 68 ppm and 34 and 41 ppm respectively. It is shown that about 1.1–1.4% of the retained ethylbenzene is metabolized to 2-ethyl-phenol. 2,4-Dimethylphenol as a metabolite of m-xylene could not be detected. It is supposed that a competitive reaction mechanism between xylenes and ethylbenzene takes place preventing m-xylene from oxidation at the aromatic nucleus. Possible carcinogenic properties of epoxides formed as intermediates must be considered.-The estimation of threshold values for the concentration of solvents in blood was attempted.     

苯,乙苯和二甲苯吸入毒物动力学

采用顶空GC/MS多离子检测技术和毒物动力学分析方法,对暴露于400ppm苯、乙苯和二甲苯中的家兔,定时观测血液毒物浓度(C_b)的时间过程。在暴露6小时期间内,C_b迅速上升,并分别维持在坪浓度2.05～4.46μg/ml处。在暴露终止后,C_b呈双相半对数-线性衰减,与二室线性毒物动力学模型计算的浓度-时间曲线吻合。     

乙苯对大鼠脑组织氧化损伤和超微结构及凋亡相关基因表达的影响

目的 观察亚慢性接触乙苯对大鼠脑组织氧化损伤、超微结构及凋亡相关基因表达的影响.方法 SD大鼠40只,随机分为4组,每组20只.暴露于0.0、433.5、4335.0和6500.0mg/m3的乙苯,6h/次,5次/周,共13周,建立大鼠乙苯亚慢性染毒模型,检测脑组织乙酰胆碱酯酶(AChE)活力、还原型谷胱甘肽(GSH)和丙二醛(MDA)含量,电子显微镜观察脑组织超微结构,实时定量聚合酶链反应(Real-time PCR)法检测脑组织B细胞淋巴瘤-2相关联X蛋白(Bax)、B细胞淋巴瘤-2(Bcl-2)、细胞色素C(Cyt C)、细胞凋亡蛋白酶(Caspase-3)、半胱天冬酶-9(Caspase-9)等基因的表达.结果 4335.0和6500.0 mg/m3剂量组大鼠脑组织内MDA含量[(2.03±0.56)、(4.17±1.31)nmol/mg pro]明显高于对照组[(1.08±0.26)nmol/mg pro],差异有统计学意义(P<0.05),各剂量组大鼠脑组织AChE活力[(0.321±0.066)、(0.276±0.031)、(0.202±0.041)U/mg]和GSH含量[(35.19±15.08)、(33.42±15.32)、(27.99±7.53)mg/g pro]均明显低于对照组[AchE活力(0.583±0.125)U/mg,GSH含量(76.38±18.41)mg/g pro],差异有统计学意义(P<0.05,P<0.05).6500.0mg/m3乙苯处理组大鼠脑组织电镜下观察可见核仁呈半月形,胞质线粒体减少,受损的神经纤维内含高电子密度的髓磷体结构,为膜性结构脂质过氧化损伤所形成.4335.0和6500.0 mg/m3剂量组Bax基因表达水平明显高于对照组和433.5 mg/m3剂量组;与对照组相比,各剂量组Cyt C、caspase-9、caspase-3基因表达水平皆明显升高,差异有统计学意义(P<0.05);各剂量组Bcl-2的基因表达水平显著低于对照组,差异有统计学意义(P<0.05).结论 乙苯可诱导大鼠脑组织氧化损伤,发生凋亡,其机制可能乙苯可导致Bax、Cyt C、caspase-9、caspase-3基因的上调和抑制Bcl-2的表达有关.     

Ethylbenzene: 4- and 13-week rat oral toxicity

Ethylbenzene was administered to groups of male and female Wistar rats by gavage for 4 (n = 5/dose/sex) and 13 weeks (n = 10/dose/sex) (OECD 408) at doses of 0 (vehicle control), 75, 250, and 750 mg/kg bodyweight/day (mg/kg bw/day), administered am/pm as half doses. In the 4-week study, ≥250 mg/kg increased serum alanine aminotransferase, total bilirubin and cholesterol, liver weights and centrilobular hepatocyte hypertrophy, and kidney weights; males also had post-dose salivation, increased urinary epithelial cell casts and cells, and hyaline droplet nephropathy. In the 13-week study, ≥250 mg/kg increased water consumption and produced post-dose salivation. Liver-related effects: increased serum alanine aminotransferase, gamma-glutamyltransferase, bilirubin, total protein, albumin and globulins, cholesterol, liver weights and centrilobular hepatocyte hypertrophy, and reduced prothrombin times. Kidney-related effects: increased serum potassium, calcium, magnesium, kidney weights, and (males only) urea and hyaline droplets in renal tubular epithelium, and reduced sodium (females only); creatinine was reduced in 750 mg/kg males. The NOAEL of ethylbenzene in these studies, based on hepatocyte hypertrophy and liver- and kidney-related clinical chemistry changes, was 75 mg/kg bw/day.     

Ototoxicity in rats exposed to ethylbenzene and to two technical xylene vapours for 13 weeks

Male Sprague–Dawley rats were exposed to ethylbenzene (200, 400, 600 and 800 ppm) and to two mixed xylenes (250, 500, 1,000 and 2,000 ppm total compounds) by inhalation, 6 h/day, 6 days/week for 13 weeks and sacrificed for morphological investigation 8 weeks after the end of exposure. Brainstem auditory-evoked responses were used to determine auditory thresholds at different frequencies. Ethylbenzene produced moderate to severe ototoxicity in rats exposed to the four concentrations studied. Increased thresholds were observed at 2, 4, 8 and 16 kHz in rats exposed to 400, 600 and 800 ppm ethylbenzene. Moderate to severe losses of outer hair cells of the organ of Corti occurred in animals exposed to the four concentrations studied. Exposure to both mixed xylenes produced ototoxicity characterized by increased auditory thresholds and losses of outer hair cells. Ototoxicity potentiation caused by ethylbenzene was observed. Depending on the mixed xylene studied and the area of the concentration–response curves taken into account, the concentrations of ethylbenzene in mixed xylenes necessary to cause a given ototoxicity were 1.7–2.8 times less than those of pure ethylbenzene. Given the high ototoxicity of ethylbenzene, the safety margin of less or equal to two (LOAEL/TWA) might be too small to protect workers from the potential risk of ototoxicity. Moreover, the enhanced ototoxicity of ethylbenzene and para-xylene observed in mixed xylenes should encourage the production of mixed xylenes with the lowest possible concentrations of ethylbenzene and para-xylene.     

Stereometabolism of ethylbenzene in man: gas chromatographic determination of urinary excreted mandelic acid enantiomers and phenylglyoxylic acid and their relation to the height of occupational exposure

Summary Ethylbenzene is an important industrial solvent and a key substance in styrene production. Ethylbenzene metabolism leads to the formation of mandelic acid, which occurs in two enantiomeric forms, and phenyl-glyoxylic acid. To decide which enantiomer is preferably formed, 70 urine samples of exposed workers were taken at the end of shifts and — after 3-pentyl ester derivatisation — gas chromatographically analysed. The R/S ratio of mandelic acid enantiomers in urine amounts to 19:1, which means that R-mandelic acid is a major metabolite and S-mandelic acid is one of the minor urinary metabolites of ethylbenzene in man. The R/S ratio is independent of ambient air concentration of ethylbenzene within the investigated range. Compared to an ethylbenzene monoexposure the height of total mandelic acid excretion is decreased in the case of coexposure to other aromatic solvents.Dedicated to Professor Dr. med. Heinz Weichardt on the occasion of his 75th birthday     

Quantitation of urinary metabolites of toluene,xylene, styrene,ethylbenzene, benzene and phenol by automated high performance liquid chromatography

Summary An automated high performance liquid chromatographic method (HPLC) for the direct determination of urinary concentrations of hippuric acid (HA), and o-, m- and p-methyl hippuric acids (MHAs), metabolites of toluene and o-, m-, and p-xylenes, and of urinary phenyl glyoxylic acid (PGA) and mandelic acid (MA), metabolites of styrene or ethylbenzene, is described. Methanol was added to urine, the mixture was centrifuged and the supernatant was injected into HPLC. A stainless-steel column packed with octadecyl silanized silicate was used and the mobile phase was a mixed solution of 5 mM potassium phosphate monobasic/acetonitrile (90/10). The method is simple and specific. Urine can be analyzed without solvent extraction. Analysis can be performed satisfactorily within 45 min for samples containing HA, MHAs, PGA and MA, and within 15 min for those containing HA, PGA and MA. Another automated HPLC method for the determination of urinary concentrations of phenylsulfate (PhS) and phenylglucuronide (PhG), metabolites of benzene and phenol, is also described. Urine was centrifuged and the supernatant was injected into HPLC. A column packed with octadecyl silicate and a mobile phase of 50 mM of potassium phosphate monobasic/acetonitrile (85/15) were used. The whole analyses and quantitative determination can be performed within 15 min for samples containing PhS and PhG in the worker's urine with a simple mobile phase. The accuracy and precision in the present methods by the use of automated HPLC were satisfactory.     

Chemical composition of smoke produced by high-frequency electrosurgery

Background  Exposure to surgical smoke during electrosurgery may be harmful to theatre personnel. This study quantified toxic compounds present and we were particularly interested in isolating toluene, ethylbenzene and xylene due to their putative carcinogenic effects. Methods  A variety of surgical procedures were studied. Smoke samples emitted during electrosurgery were collected in charcoal tubes and analysed by gas chromatography coupled with mass spectrometry. Results  Surgery involving mainly thermal decomposition of adipose tissue produced greater quantities of aldehydes and lower concentrations of toluene. In contrast, smoke generated during epidermal tissue ablation produced higher levels of toluene, ethyl benzene and xylene. Conclusion  This study demonstrated the presence of irritant, carcinogenic and neurotoxic compounds in electrosurgical smoke. This may have considerable implications for the health and safety of all involved in surgical practice, as exposure to these compounds pose potential risks to health. O.S. Al Sahaf and I. Vega-Carrascal contributed equally to this work. Aspects of this work were presented at the 31st Sir Peter Freyer Memorial Lecture and Surgical Symposium (Irish J Med Sci 2006; 175(3)S1:87).     

乙苯对大鼠尿中苯乙醇酸、苯乙醛酸水平、肾组织超微结构及线粒体凋亡相关蛋白表达的影响

目的 探讨亚慢性染毒乙苯对大鼠尿中苯乙醇酸、苯乙醛酸和肾组织超微结构及线粒体凋亡相关蛋白表达的影响.方法 SD大鼠雄性40只,随机分为对照组、低剂量组、中剂量组和高剂量组,每组10只,分别染毒0、433.5、4335.0和6500.0 mg/m~3的乙苯,每天6 h,每周5 d,共13周,建立大鼠乙苯亚慢性染毒模型;高效液相色谱法测定染毒后大鼠尿中苯乙醇酸(MA)和苯乙醛酸(PGA)水平,电镜观察肾组织的超微结构,Western blot法检测肾组织B细胞淋巴瘤-2相关联X蛋白(Bcl-2associated X protein,Bax)、B细胞淋巴瘤-2(B-cell lymphoma/leukemia-2,Bcl-2)、细胞色素C(cytochromeC,Cytc)、细胞凋亡蛋白酶(Caspase-3)、半胱天冬酶-9(Caspase-9)等线粒体凋亡相关蛋白的表达.结果 中、高剂量组大鼠尿中MA[(0.303±0.148)、(0.404±0.154)mg/L]和PGA[(0.168±0.104)、(0.174±0.092)mg/L]水平均明显高于对照组和低剂量组,差异有统计学意义(P<0.05),且MA、PGA均与乙苯外暴露剂鼍呈现一定的剂量-效应关系(r=0.827,r=0.720,P<0.05).高剂量组大鼠肾组织线粒体普遍肿胀,呈空泡状,部分线粒体嵴排列紊乱,线粒体嵴消失.中、高剂量组大鼠肾组织Bax表达水平均明显高于对照组,差异有统计学意义(P<0.05);各剂苗组大鼠肾组织Cytc和Caspase-9表达水平均明显高于对照组,差异有统计学意义(P<0.05);中、高剂量组大鼠肾组织Caspase-3表达水平均明显高于对照组和低剂量组,差异有统计学意义(P<0.05);与对照组相比,各剂量组大鼠肾组织Bcl-2表达水平均明显下降差异有统计学意义(P<0.05).结论 乙苯致大鼠肾组织细胞线粒体损伤可能是乙苯细胞毒作用机制之一,其机制可能与线粒体凋亡相关蛋白表达有关,大鼠尿中苯乙醇酸和苯乙醛酸可作为乙苯暴露后生物内剂量指标.