Occupational exposures,delivered doses and exposure limits for chromium and nickel†

The interaction of HCH (50 mg/kg) and dietary protein levels on microsomal drug metabolizing enzymes system and liver lipids were studied in the rats for 90 days. The results indicated that rats fed a lower protein diet and HCH has a higher rate of mortality, lower rate of growth and an increased liver weight. A significant induction in the hepatic microsomal aminopyrine‐N‐demethylase, p‐nitroanisole‐O‐dealkylase, benzo(a)pyrene hydroxylase and glutathione‐S‐transferase activity was observed in pesticide treated animals as compared to control animals. The pathological changes observed in liver of HCH treated animals consisted mainly of necrosis and fatty degeneration of hepatocytes. HCH also induced the significant accumulation of cholesterol, triglycerides, phospholipid and total lipid in liver in low protein diet animals. Protein accelerates the metabolism of HCH, resulting in a decrease of HCH concentration with the increase of dietary protein level. A close correlation existed between lipid accumulation, induction of drug metabolizing enzyme system and deposition of HCH in liver.     

Effect of trichloroethylene (TCE) inhalation on biotransformation enzymes of rat lung and liver

Trichloroethylene (TCE) is widely used as an industrial solvent and cleaning fluid. In the present study the toxic effects of TCE inhalation on pulmonary and hepatic biotransformation enzymes in rats have been investigated by assay of aniline hydroxylase (AH), aminopyrine-N-demethylase (APD), benzo-a-pyrene hydroxylase (BH) and glutathione-s-transferase (GST) activities and glutathione (GSH) contents in liver as well as lungs of exposed animals. In both organs phase I and phase II drug metabolizing enzymes have been found to be increased along with decrease in GSH contents following TCE inhalation. Pulmonary as well as hepatic MFO's seem to be activated by inhaled TCE probably in an attempt for its rapid detoxification and reduced glutathione is used during its biotransformation.     

DNA damage in mouse organs and in human sperm cells by bisphenol A

Abstract

The in vivo genotoxic potential of bisphenol A using the comet assay in mice and in human sperm cells in vitro without metabolizing enzymes was studied. Male mice were exposed by oral gavage to the following doses of bisphenol A (0 125, 250 and 500?mg/kg body weight). DNA damage was investigated in liver, kidney, testes, urinary bladder, colon and lungs cells. In testicular cells, a significant increase in DNA strand breaks was observed in the lowest, but not in the medium or highest dose groups. Histopathological investigation of the testicular samples did not show any treatment dose-related effects. No DNA strand breaks were observed in any of the other investigated tissues. In human sperm cells in vitro, bisphenol A did not induce DNA strand breaks.     

Comparative in vitro metabolism of chloroxylenol,chlorophene, and triclosan with rat,mouse, and human hepatic microsomes

A number of studies have reported the presence of chlorinated phenols, commonly used as antiseptics, in the environment. Chloroxylenol, chlorophene, and triclosan are three such chemicals believed to have leached into water supplies through the wastewater treatment facilities. Understanding how these compounds are metabolized is important in determining the risks of chemical exposure. In this study, we compared the in vitro metabolism of these three chlorinated phenols with rat, mouse, and human liver microsomes. The structures of the metabolites formed during the microsomal reactions were identical when rat, mouse, and human liver extracts were used, but variations existed in the kinetics of the reactions.     

苯并［a］芘对黑鲷肝脏GST活性的影响及其与肝脏代谢酶和胆汁代谢产物之间的变化关系

为探讨苯并[a]芘(B[a]P)暴露对鱼类的影响并筛选特异、敏感的生物标志物,研究了B[a]P对黑鲷(Sparus macrocephalus)肝脏谷胱甘肽-S-转移酶(GST)活性的影响,并分析了肝脏7-乙氧基异吩唑酮-脱乙基酶(EROD)、GST活性与胆汁中B[a]P典型代谢产物3-羟基-苯并[a]芘(3-OHB[a]P)3者之间及与B[a]P之间的剂量、时间-效应关系.结果显示:在B[a]P(0.5、1.0、2.0和5.0μg·L-1)暴露期间,肝脏GST活性随暴露时间总体呈"钟"形的变化趋势,在第2d时达到峰值;在第12h、1d和2d时,GST活性与B[a]P暴露浓度呈显著正相关(R12h=0.966(p<0.05)、R1d=0.953(p<0.05)、R2d=0.824(p<0.05)).与前期研究结果对比分析发现,B[a]P(0.5、1.0、2.0和5.0μg·L-1)暴露7d时,胆汁中3-OHB[a]P浓度与B[a]P暴露浓度呈显著的剂量-效应关系(R=0.943,p<0.05);黑鲷肝脏GST、EROD活性与3-OHB[a]P的对数浓度均呈显著正相关(RGST=0.740(p<0.05)、REROD=0.839(p<0.05));2.0μg·L-1B[a]P暴露后,黑鲷肝脏EROD、GST活性与3-OHB[a]P随暴露时间的变化趋势基本相同,但并不完全一致.鱼类肝脏EROD、GST与胆汁中B[a]P代谢产物3者之间的变化关系较为复杂,暴露浓度和时间是影响其变化的重要因素,肝脏GST和EROD活性比胆汁中代谢产物更易受其影响,在B[a]P的环境监测中代谢产物可能是一种更为可行的生物标志物.     

Enzymatic and cellular level effects of chromium∗

Exposure of Cr to four hepatic enzymes activities of tilapia, viz. acid‐ and alkaline phosphatases, catalase and glucose‐6‐phosphatase, was contrary to the results obtained for Cd and Ni. This is the only heavy metal investigated thus far that dramatically augmented glucose‐6‐phosphatase by approximately 83% at a concentration of 12 mg L^‐1 in vivo in lieu of the fact of an initial inhibition of approximately 45 % at a lower concentration of Cr; 6 mg L^‐1. In the case of acid phosphatase and catalase activities progressive increment was observed up to 50 and 217% respectively at a concentration of 12 mg L^‐1 Cr. On the other hand, in contrast to all the investigated enzymes interestingly alkaline phosphatase was inhibited continuously at all concentrations up to 46% at 12 mgL^‐1 Cr. In vitro experiments were contrary to the above mentioned results, whereby all hepatic enzymes were inhibited with major inhibition observed for acid phosphatase of approximately 60% from 5 mgL^‐1 Cr onwards in the system.

At cellular level, Cr exposure at a lethal dose of 12 mgL^‐1 demonstrated similar effects to that of Cd. In general, the glycogen and fat reserves were depleted while lysosomal activity is increased. As compared to the effects of Cd, the mitochondria did not indicate any prominent reflection in the formation of intramitochondrial bodies. Further, similar to Cd, the cell membrane as well as nucleus were not affected.     

离体模型预测鱼体肝脏清除速率：鲑鱼肝细胞和肝脏S9组分的比较

将离体肝细胞和肝脏S9组分用于获取鱼类的体外生物转化数据可以优化模拟评估对化学物质的生物富集作用。然而涉及2种方式之间的直接对比的研究却几乎没有。本研究采用冷藏保存的鲑鱼肝细胞来测定对于6种多环芳烃(PAHs)的体外本征清除速率。我们运用测定结果推测体内本征清除速率,并将其作为输入值输入一种充分搅匀的肝脏模型中来预测肝清除速率。将事先由体外灌流肝脏测定的速率作为参考来评价预测结果。在2种竞争结合的假说前提下,由鲑鱼肝细胞测出的肝清除速率与实现的测定结果基本一致(6种多环芳烃中的5种都保持在2.1倍差异以下)。尽管多环芳烃的高代谢率是可能的原因之一,这些发现与之前由肝脏S9组分得出的结果相似。对苯并芘这一种化合物而言,由S9数据得出的体内本征清除速率是由肝细胞得出结果的10倍左右,这一结果可能是由细胞吸收速率造成的传播限制引起的。尽管苯并芘的结果差异较大,由任何一种体外测试方法得出的体内本征清除速率结果通常是一致的。这些结果显示离体肝细胞和肝脏S9组分2种系统均可用于优化鱼类的生物富集评估,尤其对于体外反应速率较高的情况。不同系统在化工领域的应用性是否相同则需要进一步的研究工作。
精选自Kellie A. Fay, Patrick N. Fitzsimmons, Alex D. Hoffman, John W. Nichols. Comparison of trout hepatocytes and liver S9 fractions as in vitro models for predicting hepatic clearance in fish. Environmental Toxicology and Chemistry: Volume 36, Issue 2, pages 463–471, July 2017. DOI: 10.1002/etc.3572
详情请见http://onlinelibrary.wiley.com/wol1/doi/10.1002/etc.3572/full
     

Enzymatic and cellular level effects of nickel∗

The effects of Ni on hepatic enzymes of tilapia, viz. acid‐ and alkaline phosphatases, catalase and glucose‐6‐phosphatase, both under in vivo and in vitro conditions reflected the following tendencies. In vivo conditions indicated maximal increase in activity for acid phosphatase at 3.00 ppm, equivalent to 28.5%, followed by a slight decrease and increase thereafter. As for alkaline phosphatase, gradual increase in activity was observed with maximal activity at 9 ppm of Ni, equivalent to 16.8%. Catalase demonstrated similar tendencies with maximal activity at 9.0 ppm, equivalent to 101.2%. In the case of glucose‐6‐phosphatase, the tendency was the reverse with maximal inhibition at 9.00 ppm, i.e. 41.9%. In contrast to in vivo conditions, in vitro systems indicated that all investigated enzymes were inhibited in the region of 4–10% except for catalase which demonstrated a slight increase by 5–6% in activity between concentrations of 10–15 ppm of Ni but thereafter continuous inhibitory effects prevailed.

At cellular level, exposure of tilapia to a lethal dose of 9 ppm of Ni indicated not much of an adverse effect except for a slight depletion in fat and glycogen content. In the case of mitochondria, they were normal and a few large secondary lysosomes were observed. In relation to the cell membrane no dramatic change was detected.     

恩诺沙星在鲫鱼肝微粒体中的代谢及代谢关键酶的确定

抗生素因具有抗菌谱广、杀菌性强等特点使其被广泛应用于人类医药、畜牧业、农业和水产养殖业。其进入水生生物体内后,会在药物代谢酶的作用下发生代谢转化,产生生态毒性。本研究采用鲫鱼肝微粒体体外孵育法,探究恩诺沙星细胞色素P450酶作用下的代谢转化过程,并通过代谢抑制实验确定关键的代谢酶。实验结果表明,恩诺沙星体外代谢过程符合一级动力学方程,当恩诺沙星暴露浓度为1 mg·L-1时,其在肝微粒体中的消除速率常数k最大为0.00303 min-1,半衰期t1/2最短为228.8 min,应用HPLC-MS/MS技术,检测到了恩诺沙星脱乙基产物和羟基化产物;代谢抑制实验结果表明,CYP3A4在恩诺沙星代谢过程中起主要作用,是恩诺沙星代谢的关键酶。本研究结果为深入了解恩诺沙星在水生生物体内的代谢转化及其生态风险提供了基础数据。     

Electron microscopy documenting the cellular metabolic fate of Zn IONS∗

In vertebrates and invertebrates Zn exist as complexed compounds with metallothioneins. However, its cellular level effects and metabolic fates are scantly documented. In the elucidation of this fact, EM results on hepatic cellular alterations in fish under lethal dose exposure at 4.0 ppm over a week is illustrated.

A large number of lysosomes in hepatic cells prevailed on exposure to Zn in its sulfate form. Evidently, due to metal compound stress and cellular damage lysosomal activity is augmented. The lysosomes harboured digestible material, presumably the aforementioned substrates. Contrary to it, fat droplets prevailed while glycogen depletion is noticeable. Unlike the effects of Hg, the nuclei were normal with granular chromatin and prominent nucleoli. However, the mitochondria contained some small intramitochondrial bodies. Similar to the effects of Hg, the cell membrane remained intact.

In vivo enzymatic studies indicated augmentation in catalase, acid‐ and alkaline‐phosphatases, while glucose‐6‐phosphatase is inhibited. However, only alkaline‐ and glucose‐6‐phosphatases are inhibited under in vitro conditions.

Thus, it is evident that Zn enhances cellular bioenergetic requirements culminating in glycogen depletion owing to stress, concomitantly envisaging inhibition of oxidative phosphorylation in the electron transport system.     

Toxicological and ecological implications of biotransformation enzymes in the tropical teleost Chaetodon capistratus

Hepatic cytochromes P450 (phase I monooxygenases) and glutathione transferases (phase II conjugating enzymes) were investigated in Chaetodon capistratus (Linnaeus) collected in Florida and Belize in June and December 1991, respectively. These biotransformation enzymes play major roles in the detoxification of xenobiotics by converting lipophilic chemicals to more hydrophilic, readily excretable metabolites. Content of total microsomal P450 (0.501 to 0.821 nmol mg^-1 microsomal protein) and rates of NADPH-cytochrome c (P450) reductase (270.7 to 330.2 nmol min^-1 mg^-1 microsomal protein) and glutathione transferase (2.81 to 3.12 g min^-1 mg^-1 cytosolic protein) in these fish were greater than in most untreated fish species, i.e., fish that have not been exposed to PAHs (polycyclic aromatic hydrocarbons) or PCBs (polycyclic biphenyls). Ethoxyresorufin O-deethylase (EROD) rates (0.029 to 0.171 nmol min^-1 mg^-1) were also comparable to those in most untreated marine fish. Immunoblot analysis with monoclonal antibody (MAb) 1-12-3 to scup P450E (the EROD catalyst and a teleost representative of the PAH-inducible CYP1A gene subfamily) showed slight amounts of cross-reacting protein in C. capistratus liver microsomes. Hepatic CYP1A content and EROD activity did not differ significantly between fish collected in Florida and Belize, suggesting that the two sites differed little in contamination by CYP1A inducers. Immunochemical analyses with polyclonal antibodies to scup P450B (a teleost representative of the CYP2B subfamily) and human CYP3A4 cross-reacted strongly with C. capistratus hepatic proteins. The CYP2B and CYP3A subfamilies in mammals are believed to have partially evolved in response to toxic dietary allelochemicals. C. capistratus regularly feeds on terpenoid-rich gorgonian corals, suggesting that biotransformation enzymes may be involved in the metabolism of dietary allelochemicals as well as anthropogenic xenobiotics in this species.     

A comparative study of the toxicity of lead and its impact on the carbohydrate metabolism and some haematological parameters of cichlid fish,oreochromis niloticus and catfish,clarius gariepinus from saudi arabia

Fresh and healthy specimens of Oreochromis niloticus (mean weight 70.5± 1.23 g and mean length, 12.3± 1.5cm) and Clarias gariepinus (mean weight, 41.8±2.3 g and mean length 13.78 ± 1.2 cm) were exposed to heavy metal lead, ranging in concentration from 10 to 18 mg L^‐1 for O. niloticus and 20 to 28 mg L^‐1 for C. gariepinus respectively. The 96 h LC₅₀ for both the species was computed as 12.45 mg L^‐1 (O. niloticus) and 22.65 mg L^‐1 (C. gariepinus). The cichlid fish was exposed to sublethal concentration of lead (2, 4 and 6 mgL^‐1) and catfish (4, 8 and 12 mgL^‐1). The erythrocytes count, haemoglobin concentration, haematocrit and the value of serum glucose increased significantly (P < 0.01), whereas leucocytes count, serum protein and serum triglyceride after intoxication declined in both the species with the same pattern but in different quantity. After 96 h of time a significant depletion of muscle and liver glycogen was noted, being greater in muscle (16.7% in O. niloticus) and in liver (15.9% in C. gariepinus). The response of fish to lead was dose dependent.     

Retention of PCDDS and PCDFS in the liver of the rat and hamster after oral administration of a municipal incinerator fly ash extract

A single dose of an extract from 16 and 5 grams fly ash was administered orally to male rats and hamsters. In the rat 1,2,3,7,8‐PnCDD had the highest retention (41%) in the liver. The congener with the highest retention in the liver of the hamster was 2,3,4,7,8‐PnCDF (70.9%). In two oral multiple dose experiments with rats, highest liver retentions were found for 1,2,3,7,8‐PnCDD (51.7%) and 1,2,3,6,7,8‐HxCDD (59.8%). With the exception of 2,3,4,6,7‐PnCDF, all PCDDs and PCDFs retained in the liver of rat and hamster had a 2,3,7,8 chlorine substitution pattern. In both types of experiments with rats the retention of 2,3,7,8‐TCDF in the liver was very low, 1.1–2.8% of the total dose. In the liver of the hamster retention of 2,3,7,8‐TCDF was almost equal to that of 2,3,7,8‐TCDD, indicating that the hamster is probably metabolizing 2,3,7,8‐TCDF Jess efficiently than the rat. In all experiments 1,2,3,7,8‐PnCDD and 2,3,4,7,8‐PnCDF were retained in the liver more efficiently than 2,3,7,8‐TCDD. Based on first order pharmacokinetic calculations, it was found that the earlier published k_e value of 0.55 for 2,3,7,8‐TCDF in the liver of the rat was also applicable. Using the same calculations for 2,3,7,8‐TCDD (k_e = 0.029) a 30% difference was found between calculated and actual measurements, but calculated results were still within the 95% confidence limits of the actual measurements.     

Variations in carbohydrate metabolism during gonad maturation in female turbot (Scophthalmus maximus)

Several carbohydrate metabolism pathways were studied in four different tissues (liver, gonad, kidney and white muscle) of female turbot (Scophthalmus maximus) at three different stages of gonad maturation, i.e., previtellogenesis, early vitellogenesis and late vitellogenesis. During carbohydrate metabolism in the liver, the only major change noticed throughout vitellogenesis was increased glycolytic activity at early vitellogenesis. The major changes observed in the gonad during vitellogenesis were an increased use of exogenous glucose and increased gluconeogenesis, which were reflected in increased glucose levels throughout vitellogenesis accompanied by a small increase in glycogen levels. Changes observed in carbohydrate metabolism in the kidney pointed to increased gluconeogenesis during early vitellogenesis. Finally, during ovarian maturation, the muscle mobilized proteins whose constituent amino acids could have been used in other tissues either as substrates for gluconeogenesis or for protein synthesis. As an overall conclusion, changes in the carbohydrate metabolism of female turbot during maturation are quite marked in the gonad, kidney and white muscle, in contrast to other species, in which major changes have been previously reported to occur in the liver.     

Naturally high levels of zinc and metallothionein in liver of several species of the squirrelfish family from Queensland,Australia

Recently, we found that liver of squirrelfish (Holocentrus rufus) from Bermuda contains remarkably high concentrations of metallothionein (MT) and Zn. To clarify the nature and cause of the Zn accumulation, four Holocentridae species from three genera (Neoniphon sammara, Sargocentron spiniferum, Myripristis violacea, and Myripristis murdjan) were collected from a totally different area, the Great Barrier Reef, Australia. The average hepatic Zn levels in these species ranged from 67 g g^-1 (S. spiniferum) to 1000 g g^-1 (N. sammara). The intraspecies variation in the hepatic Zn level was pronounced. In both N. sammara and M. murdjan, there was a 48-fold difference between the lowest and the highest Zn concentration. Zn accumulation was closely correlated to a dramatically elevated concentration of MT in liver. In N. sammara, which possessed the highest level of MT among the investigated species, the mean hepatic MT concentration was 19 500 g g^-1. Subcellular fractionation of the liver showed that MT was responsible for the binding of up to 74% of the hepatic Zn. The concentrations of MT and Zn in gills were low, suggesting that Zn storage in fish within this family is tissue-specific. The results further indicate that the high concentrations of MT and Zn in Holocentridae liver are linked to normal physiological processes. We suggest that the Holocentridae family may be a unique model for future studies of Zn metabolism and the function of MT.     

EEDs对鱼类性激素合成途径干扰作用研究进展

环境内分泌干扰物(environmental endocrine disruptors,EEDs)是一类可以改变生物体内激素的合成、释放、运输、代谢、结合、作用或清除等一系列生物过程的外源物质。性激素的生物合成需要一系列酶的参与,体内和体外研究表明,性激素合成途径中的类固醇生成酶是EEDs通过非性激素受体介导途径发挥内分泌扰乱作用的重要靶点,性激素合成途径的扰乱可能导致生物体生殖系统受损。本文综述了EEDs对鱼类性激素合成底物和类固醇生成酶的影响、信号转导机制及其生殖危害;并对性激素合成途径中促性腺激素调控机理、多种转录因子间的相互作用、不同物种间类固醇生成酶的差异以及各内分泌轴线的相互作用研究进行了展望,以期为EEDs通过非性激素受体介导途径发挥内分泌干扰效应的机制研究提供思路。     

Humic substances. Part III. sorptive interactions with environmental chemicals†

The formation of covalent binding to DNA of a carcinogen is now widely accepted to represent a classical mechanism of tumour induction in mammals. This mechanism does not operate with metals since no covalent binding of these agents to DNA does occur. Nevertheless, somatic mutations as typical consequences of DNA‐damage have been reported to be induced by metals in various model systems. Beside DNA‐alkylation such damages can be caused by changes in the conformation of DNA or in the fidelity of DNA‐repair. The activity of the repair enzymes DNA‐polymerases is indeed impaired by many metal ions at least in vitro. It is not yet established whether these mechanisms are also important in the intact mammalian organism. Much evidence has accumulated during the last years that a disturbance of the balance of cations and especially metal ions represents another possible mechanism of tumour induction. The tumours found with high doses of chelating agents such as nitrilo‐triacetic acid (NTA) have to be discussed in this context. Since most—if not—all of the speculative mechanisms of metal carcinogenesis resemble classical pharmacological reactions the existence of a threshold level is likely. So metal carcinogenesis will not be a problem of the environmental contamination at trace levels but a problem of occupational medicine.     

Benzo[a]pyrene oxidation and microsomal enzyme activity in the mussel (Mytilus edulis) and other bivalve mollusc species from the Western North Atlantic

Analysis of subcellular fractions revealed a complement of microsomal electron transport components including reductases and heme proteins in several organs of the three bivalve species Mytilus edulis, Macrocallista maculata and Area zebra. Dithionite difference spectroscopy of CO-treated microsomes yielded spectra typical of cytochrome P-450 in digestive gland and gill, with absorption maxima at 450 nm. A time-dependent reduction of cytochrome P-450 was also observed. The levels of these components and rates of microsomal benzo[a]pyrene (BP) metabolism were highest in the digestive gland, and were very similar between species. In M. edulis there was a suggested seasonal variation in BP metabolism but no population differences in this activity or in levels of other components. Digestive gland microsomal metabolites of BP identified by HPLC retention and UV spectroscopy included BP-1.6-quinone, BP-3,6-quinone and BP-6,12-quinone, which comprised 65% of the total metabolites, and dihydrodiols and phenols, the latter products consistent with cytochrome P-450 monooxygenation and expoxide hydrolase function. However, the inconsistent dependence of BP metabolism on NADPH, and inconsistent inhibition by CO suggest that catalyst(s) additional to cytochrome P-450 may be acting in BP metabolism. Based on these results and the prominent quinone formation, we speculate that peroxidative mechanism(s) may be involved. The role of peroxidative as well as well as monooxygenase reactions in the in-vivo disposition and effects of foreign chemicals in bivalves, and also the major function of cytochrome P-450 in these bivalves, remain to be established.Some of these results have appeared in preliminary form; J. J. Stegeman, Sea Grant Annual Report, Words Hole Oceanographic Institution, p 15, 1981