Kinetics and biotransformation of benzo(a)pyrene inChironomus riparius

Uptake and depuration kinetics for benzo(a)pyrene (B(a)P) were determined for the midgeChironomus riparius (Diptera) with one and two compartment models. Nonfeeding animals were exposed to nominal 1.0μg·L^{?1 14}CB(a)P for eight hr. Depuration over eight hr was determined in animals with and without substrate. The uptake rate constant was 214+-20 hr^?1 (X+-SE, n=3), while elimination rate constants for the first four hr were 0.22 hr^?1 (with substrate) and 0.06 hr^?1 (without substrate). Biphasic depuration was observed with an initial rapid phase that lasted several hr. Approximately 10% of accumulated¹⁴C was associated with exoskeleton. As much as 50% of the accumulated B(a)P was transformed into polar compounds after one hr. Based on steady state¹⁴C concentration, an apparent bioconcentration factor of 650 was determined. The bioconcentration value based on B(a)P analysis was 200.     

双壳类水产品中(+)-anti-BPDE-DNA加合物HPLC/FD检测

目的 建立检测双壳类水产品中（+）-反-7,8-二羟基-9,10-环氧苯并（a）芘（BPDE）-DNA加合物的高效液相色谱荧光法（HPLC/FD）。方法 用组织基因组DNA提取试剂盒提取6种双壳类水产品组织中的DNA,0.1 mol/L HCl 、90 ℃酸解4 h,乙酸乙酯充分萃取酸解产物——苯并（a）芘-四醇。以CenturySIL C18-BDS色谱柱（150 mm×4.6 mm,5 μm）分离;洗脱流动相：V（甲醇）/V（水）=55/45;流速：1.0 mL/min;进样量：20 μL;激发波长：265 nm,发射波长：395 nm;荧光检测苯并（a）芘-四醇的含量。结果 该方法的检测限为0.3 ng/mL,在0.5~100 ng/mL范围内呈良好的线性关系（r²=0.9960）;日内相对标准偏差（RSD）为2.8%~4.2%,日间RSD为3.2%~5.8%;双壳类水产品中（+）-anti-BPDE-DNA含量为13.44~152.7 μg/kg,RSD为3.0%~6.5%;加标回收率为86.9%~91.6%,RSD为3.1%~7.3%。结论 该法简便、快速、灵敏度高,可用于双壳类水产品中（+）-anti-BPDE-DNA加合物的检测。     

苯并[a]芘在大鼠脑组织中分布动态观察

目的 观察[¹⁴C]标记苯并[a]芘在大鼠脑内的分布。方法 将100只SD大鼠随机分为对照组和实验组,实验组尾静脉注射[¹⁴C]标记苯并[a]芘3.7×10⁵Bq/kg,对照组注射等量生理盐水;在注射后1,6,12,24和48 h用光镜放射自显影法观察苯并[a]芘在脑内的分布情况。结果 与对照组比较,实验组大鼠脑组织注药后1 h即有苯并[a]芘银粒出现,随着时间的增加,银粒数也逐渐增加,24 h达高峰,48 h明显减少,注射后1,6,12,24,48 h银粒数分别为(17.68±1.79),(22.67±2.15),(25.79±2.55),(32.33±2.78),(18.01±1.68)粒,差异有统计学意义(F=69.67,P<0.01);银粒在脑中分布不均匀,注药后1 h主要集中在海马,6 h主要集中于大脑皮层,12 h则分布于纹状体;各时相脑组织中神经元银粒数明显高于神经胶质细胞(P<0.05)。结论 苯并[a]芘在各脑区的分布不均匀,24 h达到高峰,神经元细胞可能是苯并[a]芘靶细胞。     

Factors affecting plasma benzo[a]pyrene levels in environmental studies

Benzo[a]pyrene (BaP) is a useful indicator of exposure to polycyclic aromatic hydrocarbons (PAHs), airborne carcinogenic compounds. Radioimmunoassay was used to test for plasma BaP differences in 61 subjects divided into three groups based on geographic-demographic locale: urban-industrial, urban-residential, and outer suburban. The results showed that the urban-industrial area participants had a significantly higher mean plasma BaP level than did the outer suburban subjects. The urban-residential subjects did not have a significantly different mean plasma benzo[a]pyrene level from either of the other two groups. Obesity, as measured by Quetelet's index, was found to have a significant correlation with BaP levels. These results indicate that radioimmunoassay of plasma for BaP may be used successfully to judge environmental exposure to PAHs, provided physiological considerations such as obesity are taken into account.     

Toxicokinetics of sediment-sorbed benzo[a]pyrene and hexachlorobiphenyl using the freshwater invertebrates Hyalella azteca,Chironomus tentans,and Lumbriculus variegatus

This study investigated the effect of long-term sediment aging on the toxicokinetics of benzo[a]pyrene (BaP) and hexachlorobiphenyl (HCBP) using three freshwater benthic invertebrates. Hyalella azteca, Chironomus tentans, and Lumbriculus variegatus were exposed to BaP- and HCBP-spiked sediments that were aged for 7 d or 1.5 years. The toxicokinetics of the two compounds were determined for each test organism using a two-compartment model. The modeling of BaP was more complex because biotransformation was included within the model. The results of this study showed that the HCBP uptake clearance rates (k(s)) for each species were generally an order of magnitude greater than those determined for BaP and this difference was most likely due to preferential and rapid binding of BaP to sediment particles. Overall, the bioavailability of HCBP in spiked sediments tended to decrease with duration of aging, based on k(s) values and bioaccumulation factors (BAFs). However, the decreases in bioavailability appear to be species specific. Benzo[a]pyrene did not decline in bioavailability for the species tested because it may resist movement into the micropores of the sediment due to its large size. In addition to the bioassays, this article outlines a method for toxicokinetic modeling of biotransformed compounds and methods for statistical comparisons of kinetic parameters (i.e., k(s), k(d)...) and BAF values.     

Chemical and biological availability of sediment-sorbed benzo[a]pyrene and hexachlorobiphenyl

This study examined the chemical and biological availability of two nonpolar organic compounds, benzo[a]pyrene (BaP) and hexachlorobiphenyl (HCBP), from a spiked sediment that was aged for varying amounts of time. Chemical availability was evaluated using four different solvent combinations to extract chemicals from the sediment. The extractability of BaP and HCBP from sediment using traditional solvents was then compared to the transfer efficiency (TE) of a benthic invertebrate (Lumbriculus variegatus) to relate chemical extractability to bioavailability in the organisms. Results indicated that water was the solvent that best approximated bioavailability for BaP, whereas comparisons for HCBP were inappropriate, because TE values exceeded 100%. The inability to obtain a reasonable TE estimate for HCBP was most likely due to the fact that the oligochaetes received a major portion of their uptake from interstitial water instead of ingestion of sediment particles, which invalidated an important assumption of the TE model. Overall, the results of this study indicate that exhaustive chemical extractions may be an inaccurate representation of the bioavailable fractions for some contaminants.     

苯并[a]芘与铅联合神经毒性的细胞学研究

目的苯并[a]芘(BaP)、铅及其联合作用对体外神经元的毒性及细胞凋亡率的影响.方法取8日龄SD大鼠小脑粒细胞培养,按以下分组进行处理空白对照组;溶剂对照组;低浓度铅染毒组;高浓度铅染毒组;低浓度BaP染毒组;高浓度BaP染毒组;低浓度铅+低浓度BaP染毒组;低浓度铅+高浓度BaP染毒组;高浓度铅+低浓度BaP染毒组;高浓度铅+高浓度BaP染毒组;高、低浓度的BaP染毒分别为BaP50μmol/L+S9-mix和BaP5μmol/L+S9-mix,高、低浓度的铅染毒分别为50和5μmol/L的PbAc,溶剂对照组用等量DMSO平行处理,空白对照组不作处理.染毒90min,胰酶消化法收集标本.台盼蓝染色法检测存活率;DNA断点末端核糖核酸转移酶地高辛标记(TUNEL)法检测大鼠小脑粒细胞凋亡率,并对细胞存活率与凋亡率进行相关分析.结果各染毒组细胞存活率均低于对照组,高剂量组降低程度高于低剂量组,联合染毒组降低程度高于单独染毒组(P<0.05～P＜10E-7).各染毒组细胞凋亡率显著升高,高剂量组升高程度高于低剂量组,联合染毒组升高程度高于单独染毒组(P＜0.001～P＜10E-9).细胞凋亡率与存活率间呈负相关(r=-0.76125,P＜0.05).结论 BaP、铅均有一定的体外神经毒性,二者联合作用可使毒性增强.细胞凋亡可能是BaP引起体外神经毒性的机制之一.     

婴幼儿奶粉中苯并[a]芘检测技术研究及含量调查

目的建立婴幼儿奶粉中苯并[a]芘检测技术,并对市售奶粉中苯并[a]芘含量进行调查分析。方法婴幼儿奶粉在碱性条件下用乙醚-石油醚(1∶1,V/V)提取,然后用1.5 mol/L氢氧化钾乙醇溶液皂化,固相萃取柱净化后,经DB-EUPAH色谱柱(20 m×0.18 mm×0.14μm)分离后气相色谱质谱法检测,D12-苯并[a]芘内标定量。结果当婴幼儿奶粉中苯并[a]芘加标0.3、1.0和5.0μg/kg时,平均回收率分别为116.7%、86.0%、96.4%,相对标准偏差为10.5%、4.2%和4.4%(n=6)。方法定量限为0.3μg/kg,检出限为0.1μg/kg,采用本方法对市售的40份国产及进口婴幼儿奶粉进行测定,苯并[a]芘含量范围为<0.1~0.25μg/kg,检出率为32.5%。结论本方法简便快速准确,净化效果好,灵敏度高,满足婴幼儿奶粉中苯并[a]芘检测要求。目前市售婴幼儿奶粉中苯并[a]芘含量处于较低水平。     

Biochemical response of anthracene and benzo [a] pyrene in milkfish Chanos chanos

Polycyclic aromatic hydrocarbons (PAHs) are common toxic pollutants found in the aquatic environment, and the assessment of their impact on biota is of considerable concern. The aim of the present research was to study the acute toxicity, bioaccumulation and biochemical response of milkfish Chanos chanos (Forsskal) to two selected PAHs: anthracene and benzo [a] pyrene. Acute toxicity test results were evaluated by the Probit analysis method and 96h LC(50) values for C. chanos exposed to anthracene was 0.030mgl(-1) and 0.014mgl(-1) for benzo [a] pyrene. Bioaccumulation concentration of anthracene was high when compared to benzo [a] pyrene. Biomarkers indicative of neurotoxicity (acetylcholinesterase, AchE), oxidative stress (lipid peroxidation, LPO and catalase, CAT) and phase II biotransformation of xenobiotics (glutathione S transferase, GST and reduced glutathione, GSH) were measured to assess effects of selected PAHs. Anthracene and benzo [a] pyrene increase LPO and CAT level of C. chanos suggesting that these PAHs may induce oxidative stress. Both the PAHs inhibited AchE indicating that they have at least one mechanism of neurotoxicity in common: the disruption of cholinergic transmission by inhibition of AChE. An induction of C. chanos glutathione S-transferase (GST) activity was found in fish exposed to benzo [a] pyrene, while an inhibition was observed after exposure to anthracene. These results suggest that GST is involved in the detoxification of benzo [a] pyrene, but not of anthracene.     

Relationship between metabolism and bioaccumulation of benzo[a]pyrene in benthic invertebrates

The potential influence of polycyclic aromatic hydrocarbon (PAH) metabolism on bioaccumulation is well accepted, but rarely has been examined in many species of benthic invertebrates that commonly are found in contaminated sediments, or used in bioaccumulation or toxicity tests. In this study, the relative ability of 11 species of near-shore benthic invertebrates to metabolize and bioaccumulate a model PAH, benzo[a]pyrene (B[a]P), was evaluated. Species examined included six polychaetes (Clymenella torquata, Nereis virens, Nereis succinea, Nephtys incisa, Spio setosa and Cirriformia grandis), three bivalves, (Macoma balthica, Mya arenaria, and Mulinia lateralis), and two amphipods (Ampelisca abdita and Leptocheirus plumulosus). After 7 d of exposure to sediments spiked with radiolabeled B[a]P, metabolites comprised between 6.1% (Clymenella torquata) to 85.7% (Nereis succinea) of total accumulated B[a]P, with individual species from the same phylogenetic groups showing large differences in their ability to metabolize this PAH. Bioaccumulation factors (B[a]P in tissue/B[a]P in sediment) were inversely related to the species' ability to metabolize PAH, highlighting the importance of considering metabolism when interpreting bioaccumulation across several species. These data argue strongly against the continued use of the large polychaete Nereis virens, one of the species showing the greatest ability to metabolize B[a]P, for bioaccumulation testing when PAHs are being considered. Other commonly used test species had relatively low levels of metabolism (Ampelisca abdita, Leptocheirus plumulosus, and Macoma balthica), supporting their use in evaluation of potential PAH impact on the environment.     

Vitamin A status and metabolism of benzo[a]pyrene in the rat

Male Sprague-Dawley rats were maintained on a vitamin A-deficient diet for a period of five weeks. At the end of that time, hepatic cytochrome P450 levels in vitamin A-deficient rats were 65% that of rats fed a complete diet. However, the hepatic rate of benzo[a]pyrene metabolism was significantly greater (2 times) in vitamin A-deficient rats compared with those fed a complete diet. The pattern of metabolites separable by thin-layer chromatography was similar in both groups of rats. Benzo[a]pyrene induced its own metabolism by a slightly greater amount in the vitamin-sufficient rats, but it was not to the level of the deficient group, although the levels of cytochrome P450 were still below those of the deficient rats. In discussing lung microsomes, benzo[a]pyrene pre-treatment of deficient rats resulted in slightly elevated levels of cytochrome P450 and a slightly greater rate of metabolism of benzo[a]pyrene compared with rats fed the complete diet.     

磷酸化Rb在苯并[a]芘致皮质神经元凋亡中的作用

目的探讨磷酸化视网膜母细胞瘤蛋白（phospho-retinoblastoma protein,p-Rb）在苯并[a]芘致神经元凋亡过程中的作用。方法用CCK-8试剂检测细胞活性;Annexin—V／PI双染法检测细胞凋亡率,免疫荧光细胞化学染色观察p．Rb表达,免疫印记法（Western-blot）检测p—Rb的表达情况。结果与对照组相比,各染毒组神经元活性降低（P〈0．05）,凋亡率增高（P〈0．05）,p-Rb表达量增高（P〈0．05）,2μmol／L组加入抑制剂后细胞活性增强（P〈0．05）,凋亡率下降（P〈0．05）,p—Rb阳性细胞数减少（P〈0．05）,p-Rb表达量降低（P〈0．05）。结论苯并[a]芘可引起磷酸化Rb水平升高,是苯并[a]芘致神经元凋亡的可能机制。     

Uptake and elimination of benzo[a]pyrene in the terrestrial isopod Porcellio scaber

In isopods from contaminated sites relatively low levels of high molecular weight polycyclic aromatic hydrocarbons (PAHs) have been observed, which may be caused by either a low bioavailability or a high elimination rate. To shed light on this, the uptake and elimination rates of benzo[a]pyrene were estimated for the isopod Porcellio scaber. The isopod was fed contaminated food (100 g benzo[a]pyrene/g dwt) for seven weeks followed by four weeks of untreated food. The hindguts of the animals were removed prior to analysis to exclude food material from the body. Benzo[a]pyrene concentrations were log-normally distributed among the individuals. The high inter-individual variation in benzo[a]pyrene content could not be explained from differences in sex, the estimated amount of food in the hindgut, or the body weight. A one-compartment model fitted to the isopod concentrations estimated an assimilation rate of 2.9 g benzo[a]pyrene/g dwt day, an elimination rate constant of 1.1/day and an equilibrium concentration of 2.5 g benzo[a]pyrene/g dwt. According to the model 68% of the isopod population had an equilibrium concentration between 1.0 and 7.2 g benzo[a]pyrene/g dwt day with a benzo[a]pyrene half-life ranging between 0.4 and 1.3 days. The assimilation efficiency was estimated at 20 to 40% of the ingested benzo[a]pyrene. The tissue distribution of benzo[a]pyrene was investigated in a separate experiment. Trace levels of benzo[a]pyrene were detected in haemolymph samples, demonstrating absorption and transport of the compound in the isopod. It is concluded that dietary benzo[a]pyrene is available for uptake to the isopod and that low residues of the compound observed in field isopods are the result of a high elimination rate rather than a reduced bioavailability. As PAHs from soil appear to be available to soil invertebrates, the widespread contamination of the soil from atmospheric emissions is of some concern, especially since the observed elimination may be linked to metabolic activation of PAHs.