Excretion and Tissue Distribution Properties of PCB-126 for Establishing a Bioaccumulation Model in Mice

Abstract

Polychlorinated biphenyls (PCBs) are persistent environmental pollutants, and their harmful effects on humans and animals are a major concern. Although the mechanisms of PCB toxicity have been studied, and they are known to largely accumulate in adipose tissue and liver, no therapy for PCB exposure has been established. To develop excretion-enhancing methods or antidotes for PCBs, animal models reflecting actual PCB bioaccumulation should be used. To establish such a model, we administered four levels of [³H]-labeled PCB-126 (710.4 × 10⁴, 142.1 × 10⁴, 28.4 × 10⁴, and 5.7 × 10⁴ dpm) to mice and investigated their excretion and tissue distribution. Lindane was used as a readily excreted comparator. 28.4 × 10⁴ or 5.7 × 10⁴ dpm [³H]PCB-126 resulted in excretion and tissue-distribution levels that were close to the detection limit. Administration of the maximum dose of [³H]PCB-126 resulted in continual excretion in feces and urine over the 8-day experimental period. In the mouse administered 142.1 × 10⁴ dpm [³H]PCB-126, the fecal and urinary excretion were reduced to a constant low level by day 8 after exposure, suggesting that the distribution of [³H]PCB-126 into the tissues had almost been completed. Our results suggest that mice administered 142.1 × 10⁴ dpm [³H]PCB-126 could be suitable as a PCB-126 bioaccumulation model for research to facilitate methods to enhance PCBs excretion and to develop therapies for PCBs toxicity.

INTRODUCTION

Polychlorinated biphenyls (PCBs) have been widely used as insulators, electrical energy transformers, heaters, and coolers in industrial fields¹⁾ because of their excellent chemical stability and electrical insulation. PCBs comprise approximately 200 isomers, some of which exhibit dioxin-like toxic effects (dioxin-like PCBs). PCBs exhibit high environmental persistence and bioaccumulation, and their harmful effects on humans and animals are a major concern. In the 1970s, PCB contamination occurred in Japan, Taiwan, Belgium, and other countries^2–4); the most representative PCB poisonings have been “YUSHO” in Japan and “Yuchen” in Taiwan. These induced various health effects including chloracne and hyperlipidemia^5,6) due to the ingestion of PCB-contaminated rice oil. Therefore, PCBs have been regulated for manufacture, use, and transport by the Stockholm Convention on Persistent Organic Pollutants.⁷⁾

PCBs have been reported to exhibit strong carcinogenicity, teratogenicity, immunotoxicity, and endocrine-disrupting effects.^8–11) Aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor, is known to play an important role in the toxicity of PCBs because PCB toxicity is abolished in AhR-knockdown cells and knockout mice.^12–14) AhR is activated by ligands including PCBs, dioxins, polyaromatic hydrocarbons, heterocyclic amines, and tryptophan metabolites and induces the expression of AhR-regulated genes such as cytochrome P450 (CYP) 1A1, CYP1A2, and CYP1B1,^15–17) which are enzymes involved in PCB metabolism. In addition, reactive oxygen species (ROS) can be generated. Because PCBs are minimally metabolized, ROS generation can continue for a long time¹⁸⁾ and can result in oxidative stress followed by damage to DNA, proteins, and lipids and the release of proinflammatory cytokines. In fact, YUSHO patients showed high blood ROS levels compared with a non-exposed group.¹⁹⁾

Like dioxins, PCBs exhibit high lipophilicity and capacity for binding to the CYP1A2 protein, which functions as a reservoir for dioxins in the liver. PCBs therefore mainly accumulate in the adipose tissue and liver.^20,21) To develop therapies for PCB exposure and toxicity, it is necessary to establish methods to enhance PCB excretion by using appropriate animal models. Intraperitoneally or orally administered PCB-136 is excreted in urine and feces of rats, dogs, and monkeys.^22,23) In humans, PCBs are excreted mainly in feces and sebum, and they are excreted slightly in urine.^24,25) Therefore, PCBs are excreted primarily in feces and sebum with minor excretion in urine. Methods for enhancing PCB excretion from experimental animals have commonly used activated charcoal and dietary fiber.^26–28) Although these have the ability to adsorb PCBs released to the intestine by the gastrointestinal circulation, and these absorbates are finally excreted in feces, the amount of non-metabolized PCBs released to the bile duct and intestine can be very small. Thus, another, more effective, approach is needed to promote PCB release from the liver and adipose tissue. Animal models that reflect actual PCB bioaccumulation should be used; however, currently no such model has been established.²⁹⁾

Here, we administered four amounts of radiolabeled PCB-126 (710.4 × 10⁴, 142.1 × 10⁴, 28.4 × 10⁴, and 5.7 × 10⁴ disintegrations per minute [dpm]) to mice and analyzed the toxicokinetics of PCB-126 in comparison with lindane as a reference chemical that exhibits low bioaccumulation. Only in the mouse administered 142.1 × 10⁴ dpm [³H]PCB-126 did the fecal and urinary excretion decrease to a constant low level by day 8 after administration. In addition, [³H]PCB-126 accumulated largely in the adipose tissue and liver. Our results suggest that mice administered 142.1 × 10⁴ dpm [³H]PCB-126 could be used as a PCB bioaccumulation model.

MATERIALS AND METHODS

Chemicals

[¹⁴C]lindane and [³H]PCB-126 were purchased from American Radiolabeled Chemicals, Inc. (St. Louis, MO, USA). They had specific activities of 5 mCi (1.11 × 10¹⁰ dpm)/mmol and 5 Ci (1.11×10¹³ dpm)/mmol, respectively, and both had radiochemical purity >97%. Both [¹⁴C]lindane and [³H]PCB-126 were diluted with olive oil. Soluene-350 tissue solubilizer and Hionic-Fluor solution were purchased from Packard Bioscience (Groningen, The Netherlands). Clear-sol II scintillator reagent was purchased from Nacalai Tesque (Kyoto, Japan). All other chemicals used were of the best commercially available grade.

Animals

Eleven-week-old C57BL/6J mice were purchased from Jackson Laboratory and were housed in a room maintained at 23 ± 2°C with 50% ± 10% humidity and a 12 h light–dark cycle (lights on from 8:00 a.m. to 8:00 p.m.). Food and water were provided ad libitum. All animal care and handling procedures were approved by the Institutional Animal Care and Use Committees of Gifu Pharmaceutical University. All efforts were made to minimize both suffering and the number of animals used. At the time of the study, mice were housed individually in stainless-steel metabolic cages designed for the separate collection of feces and urine. CE-2 (CLEA, Tokyo Japan) was used as the diet in all experiments.

Animal Experiments

Each dose of both chemicals was administered to a single mouse. All mice intraperitoneally injected on day 0 with one of four doses of [³H]PCB-126 (208.91, 41.78, 8.36, or 1.67 ng) or [¹⁴C]lindane (186.12, 37.22, 7.44, or 1.49 μg), equivalent to 710.4 × 10⁴, 142.1 × 10⁴, 28.4 × 10⁴, and 5.7 × 10⁴ dpm. Total urine and total feces were collected on days 2, 4, 6, and 8 following the [¹⁴C]lindane or [³H]PCB-126 treatment. All animals were euthanized on day 8, and blood samples were collected. Various tissues were then removed and weighed. Fecal samples were air-dried and then weighed. All collected blood samples were immediately centrifuged, and the serum in the supernatant was transferred to another tube for measurement of ³H or ¹⁴C content by liquid scintillation counting.

Detection of Radioactivity

Fecal samples were air-dried and homogenized; then they were treated with isopropanol and 30% H₂O₂ as a bleaching agent. All tissues, serum, and fecal samples were then dissolved in Soluene-350 tissue solubilizer. Hionic-Fluor solution was then added, and ³H or ¹⁴C radioactivity was quantified with a liquid scintillation counter (Nippon Raytech Co., Tokyo, Japan). Urine samples were mixed with Clear-sol II (Nacalai Tesque, Inc., Kyoto, Japan) for measurement of radioactivity by the liquid scintillation counter. The blank value was quantified before the measurement of samples.

RESULTS

Analysis of Fecal Excretion Levels of [³H]PCB-126 and [¹⁴C]lindane

Previously, we investigated the toxicokinetics of [³H]2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in male mice early after intraperitoneal exposure to establish a bioaccumulation model of TCDD, and we demonstrated that the distribution and the daily excretion of [³H]TCDD in urine and feces reached a constant from post-exposure day 8 onward.³⁰⁾ Similarly, to establish a bioaccumulation model of PCBs, in the current study we investigated the tissue distribution and excretion of [³H]PCB-126, one of the most toxic PCBs, for 8 days after exposure. We report the excretion levels in two ways: the absolute amounts and the percentage of administered doses.

In absolute amounts, fecal excretion levels of [³H]PCB-126 increased in a dose-dependent manner. The mouse administered 710.4 × 10⁴ dpm showed the highest fecal excretion level compared with other groups (Table 1), but the amounts excreted decreased each day (Table 1 and Fig. 1A). In terms of the percentage of administered doses, the mouse administered 5.7 × 10⁴ dpm excreted the highest percentage on day 2 compared with the other mice (Fig. 1A). However, in the mice administered 5.7 × 10⁴ and 28.4 × 10⁴ dpm, the fecal excretion levels were around the detection limit (almost the same value as the blank) except for days 2 and 4 (Table 1). In the mouse administered 142.1 × 10⁴ dpm, the daily fecal excretion level was maximal on day 2 (2.1 × 10⁴ dpm or 1.5% of administration) and gradually decreased from day 2 to day 8, and [³H]PCB-126 was sufficiently detectable on each day (Table 1 and Fig. 1A). Moreover, the cumulative fecal excretion level almost reached a plateau on day 6 and increased little from day 6 to day 8 (Table 1 and Fig. 1B). These results indicated that a dose of 142.1×10⁴ dpm was sufficient to detect excreted [³H]PCB-126 in feces, and the fecal excretion reached a relatively constant low level on day 8.

Table 1. The absolute amounts of fecal and urinary excretion of [³H]PCB-126 and [¹⁴C]lindane

	[3H]PCB-126					[14C]lindane
Administration dose (dpm)	5.7 × 104	28.4 × 104	142.1 × 104	710.4 × 104		5.7 × 104	28.4 × 104	142.1 × 104	710.4 × 104
Daily fecal excretion level(dpm)
Day 2	5078	4067	20908	147355		863	905	1612	6416
Day 4	1241	3555	13953	82652		126	111	124	41
Day 6	453	N.D.	6235	67889		396	312	104	457
Day 8	N.D.	453	1974	58647		554	382	637	503
Cumulative fecal excretion level(dpm)
Day 2	5078	4067	20908	147355		863	905	1612	6416
Day 4	6318	7622	34860	230007		989	1016	1736	6457
Day 6	6771	7622	41096	297896		1385	1328	1840	6914
Day 8	6771	8075	43070	356543		1939	1710	2477	7417
Daily urinary excretion level(dpm)
Day 2	911	2138	7286	103055		2096	4080	11744	60179
Day 4	1241	1924	7495	66971		247	596	1419	2608
Day 6	1577	2260	6743	64545		240	366	482	860
Day 8	1667	1666	5005	60173		158	234	318	288
Cumulative urinary excretion level(dpm)
Day 2	911	2138	7286	103055		2096	4080	11744	60179
Day 4	2152	4062	14781	170026		2343	4676	13164	62787
Day 6	3728	6322	21524	234571		2583	5042	13646	63647
Day 8	5395	7988	26529	294745		2741	5276	13963	63934

dpm: Disintegrations per minute; N.D.: Not detected

Fig. 1

Fecal Excretion of [³H]PCB-126 and [¹⁴C]lindane

Mice were intraperitoneally injected with one of four doses of [³H]PCB-126 or [¹⁴C]lindane on day 0. (A, C) Daily fecal excretion levels of [³H]PCB-126 and [¹⁴C]lindane shown as the percentage of administered dose. (B, D) Cumulative fecal excretion levels of [³H]PCB-126 and [¹⁴C]lindane shown as the percentage of administered doses.

We further examined the daily fecal excretion of the same radioactive dosage of [¹⁴C]lindane as a positive control that was rapidly excreted from the body. For all tested dosages, daily fecal excretion levels reached a maximum on day 2 (0.1 × 10⁴ to 0.6 × 10⁴ dpm or 0.09% to 1.52% of the administered doses) and decreased sharply from days 2 to 4 (Table 1 And Fig. 1C). Moreover, in absolute amounts, the cumulative fecal excretion levels of [¹⁴C]lindane increased only slightly from days 2 to 8 in all groups (Table 1 and Fig. 1D). These results indicated that most fecal excretion of [¹⁴C]lindane occurred by day 2, and little [¹⁴C]lindane was excreted in feces from day 4 onward.

Analysis of Urinary Excretion Levels of [³H]PCB-126 and [¹⁴C]lindane

We next investigated the levels of [³H]PCB-126 and [¹⁴C]lindane excretion in urine. In mice administered either 5.7 × 10⁴ or 28.4 × 10⁴ dpm of [³H]PCB-126, the urinary excretion levels were around the detection limit during the experimental period (Table 1 and Fig. 2A). The mouse administered 710.4 × 10⁴ dpm showed the maximum urinary excretion level on day 2, and the daily urinary excretion level gradually decreased from days 2 to 8 (Table 1 and Fig. 2A). Moreover, the cumulative urinary excretion level in the mouse administered 710.4 × 10⁴ dpm reached 30 × 10⁴ dpm or 4.2% of administration on day 8 (Table 1 and Fig. 2B). The excretion amount of [³H]PCB-126 in the urine (Table 1 and Fig. 2) was lower than that in the feces (Table 1 and Fig. 1).

Fig. 2

Urinary Excretion Level of [³H]PCB-126 and [¹⁴C]lindane

Mice were intraperitoneally injected with one of four doses of [³H]PCB-126 or [¹⁴C]lindane on day 0. (A,C) Daily urinary excretion levels of [³H]PCB-126 and [¹⁴C]lindane shown as a percentage of administered doses. (B,D) Cumulative urinary excretion levels of [³H]PCB-126 and [¹⁴C]lindane shown as a percentage of administered doses.

In all mice administered [¹⁴C]lindane, daily urinary excretion levels were maximal (0.2 × 10⁴ to 6 × 10⁴ dpm or 0.9% to 3.7% of administered doses) on day 2 and decreased sharply from days 2 to 4 (Table 1 and Fig. 2C). Although this pattern of urinary excretion was similar to that of fecal excretion, the amount of [¹⁴C]lindane excreted in urine was higher than that excreted in feces (Table 1 and Fig. 1C, 2C). Moreover, the cumulative urinary excretion levels of [¹⁴C]lindane were increased slightly or not changed from days 2 to 8 in all groups (Table 1 and Fig. 2D). These results indicated that urine, rather than feces, was the major excretion route of lindane.

Investigation of [³H]PCB-126 Concentrations in the Tissues

To determine the optimal [³H]PCB-126 doses that reflect the actual tissue accumulation properties of PCBs, we investigated the concentration of [³H]PCB-126 in the serum and tissues including the major accumulation tissues (adipose tissue and liver). The concentration of [³H]PCB-126 increased in a dose-dependent manner in all tested tissues (Fig. 3A and B). The concentrations of [³H]PCB-126 in the livers and adipose tissue of all groups were shown in Fig. 3A. In the other tissues, [³H]PCB-126 was also detectable in the mice administered 710.4 × 10⁴ and 142.1 × 10⁴ dpm (Fig. 3B); however, the concentrations of [³H]PCB-126 in these tissues were lower than those in the liver and adipose tissues. In contrast, in the mice administered 28.4 × 10⁴ and 5.7 × 10⁴ dpm, [³H]PCB-126 levels were around the detection limit in the lung, brain, heart, and kidney (approximately 0.005 × 10⁴ to 0.015 × 10⁴ dpm/g tissue) (Fig. 3B). These results indicated that doses of PCB-126 of 142.1 × 10⁴ dpm or higher would be necessary to investigate the effects of test chemicals on its toxicokinetics in its target organs.

Fig. 3

[³H]PCB-126 Concentration in Tissues and Serum in from Mice Administered [³H]PCB-126

Four mice were each intraperitoneally injected with one of four doses of [³H]PCB-126 on day 0. After the mice were euthanized on day 8, the tissues were removed. The concentrations of [³H]PCB-126 in (A) the liver and adipose tissue, and (B) the lung, brain, heart, kidney, thymus, muscle, and serum are shown.

DISCUSSION

The toxicokinetics of some PCB isomers have been reported. For example, PCB-136 and PCB-153 are metabolized and excreted in the urine and feces when intravenously administered to rats.²³⁾ On day 1 after administration, 2% and 0.2% of the PCB-136 and PCB-153 administered, respectively, are excreted in the urine, and 40% and 30% of the doses are excreted in the feces.²³⁾ In guinea pig, intraperitoneally administered PCB-187 is maximally excreted in the feces on day 2.³¹⁾ These lines of evidence suggest that the degree of chlorination can affect the rate of metabolism and excretion of PCBs.

In order to develop antidotes and detoxification methods for PCBs, it will first be necessary to establish bioaccumulation models of PCBs; however, to our knowledge, no such model has been established. In the current study, we proposed a PCB bioaccumulation model using mice administered [³H]PCB-126. Our experiments were performed with N = 1 because PCB-126 is a class I designated chemical substance and is restricted in use. However, our results showed dose-dependent excretion levels. And urinary and fecal excretion and tissue distribution of [³H]PCB-126 were all stable 8 days after administration of a dose of 142.1 × 10⁴ dpm. An excess dose of [³H]PCB-126 administration resulted in persistent excretion in feces, perhaps because it was in excess of the volume of distribution and may have overflowed from the adipose tissue and liver, the major storage tissues. In contrast, an insufficient dose resulted in low excretion and tissue-distribution levels close to the detection limit.

Both lindane and PCB-126 are organochlorine compounds, but they have different excretion characteristics: lindane is excreted mainly in urine,³²⁾ whereas PCB-126 is excreted mainly in feces.³³⁾ More than 99% of the composition of lindane, a neurotoxic chemical used as an agricultural and residential pesticide, is the γ-benzene hexachloride (BHC) isomer. BHC is an organochlorine compound with nine stereoisomers, each of which exhibits different characteristics. For example, the γ-BHC isomer has the most pronounced insecticidal properties,³⁴⁾ whereas the β and ɛ isomers are non-toxic to insects.³⁵⁾ In mammals, both the γ and β isomers induce liver enlargement.³⁶⁾ Although γ-BHC is known for its extreme acute toxicity, it does not accumulate in the body and is rapidly excreted into the urine. In the current study, we therefore used lindane as a positive control for an excreted for a chlorinated compound that excretes quickly. Our results demonstrated that lindane was excreted mainly in urine early after its administration. This result is consistent with previous report³⁷⁾ and showed that lindane was rapidly distributed to the whole body by 5 min after exposure. Approximately 50% of the dose was excreted in urine by day 1 after exposure.³⁷⁾ Therefore, in our experiments, most of the lindane was probably excreted by day 2 after exposure.

The fecal [³H]PCB-126 excretion plateaued at a low level by day 8 in the mouse administered 142.1 × 10⁴ dpm. Moreover, the fact that the urinary excretion level of [³H]PCB-126 was lower than the fecal excretion level was consistent with the results of previous reports about PCBs, polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs).^23,30,38) The fact that PCBs, PCDDs, and PCDFs are preferentially excreted in feces instead of urine might be attributed to their high lipophilicity and limited metabolism.

In summary, we investigated the fecal and urinary excretion of [³H]PCB-126, which showed the same excretion pattern as other PCBs in previous reports. We proposed that administration of 142.1 × 10⁴ dpm [³H]PCB-126 might be a suitable for PCB-126 bioaccumulation model, because the fecal and urinary excretion reached a constant low level by day 8 after administration, and [³H]PCB-126 largely accumulated in the adipose tissue and liver, although there were detectable levels in other tissues. This model could contribute to establishment of excretion-enhancing methods and subsequent development of therapy for PCB toxicity.

Acknowledgments

We thank Takuma Iguchi (Osaka University) for excellent technical assistance in the toxicokinetics study. This study was financially supported by JST SPRING (JPMJSP2142 to S.T.) from the Japan Science and Technology Agency.

Conflict of interest

The authors declare no conflict of interest.

REFERENCES

• 1)    Erickson  MD,  Kaley  RG 2nd. Applications of polychlorinated biphenyls. Environ. Sci. Pollut. Res. Int., 18, 135–151 (2011).
• 2)    Hsu  ST,  Ma  CI,  Hsu  SK,  Wu  SS,  Hsu  NH,  Yeh  CC,  Wu  SB. Discovery and epidemiology of PCB poisoning in Taiwan: a four-year followup. Environ. Health Perspect., 59, 5–10 (1985).
• 3)    Masuda  Y,  Kuroki  H,  Haraguchi  K,  Nagayama  J. PCB and PCDF congeners in the blood and tissues of yusho and yu-cheng patients. Environ. Health Perspect., 59, 53–58 (1985).
• 4)    van Larebeke  N,  Hens  L,  Schepens  P,  Covaci  A,  Baeyens  J,  Everaert  K,  Bernheim  JL,  Vlietinck  R,  De Poorter  G. The Belgian PCB and dioxin incident of January-June 1999: exposure data and potential impact on health. Environ. Health Perspect., 109, 265–273 (2001).
• 5)    Kuratsune  M. An Abstract of Results of Laboratory Examinations of Patients with Yusho and of Animal Experiments. Environ. Health Perspect., 1, 129 (1972).
• 6)    Guo  YL,  Yu  ML,  Hsu  CC,  Rogan  WJ. Chloracne, goiter, arthritis, and anemia after polychlorinated biphenyl poisoning: 14-year follow-Up of the Taiwan Yucheng cohort. Environ. Health Perspect., 107, 715–719 (1999).
• 7)    Lallas  PL. The Stockholm Convention on Persistent Organic Pollutants. Am. J. Int. Law, 95, 692–708 (2001).
• 8)   National Toxicology Program. Toxicology and carcinogenesis studies of a binary mixture of 3,3′,4,4′,5-pentachlorobiphenyl (PCB 126) (Cas No. 57465-28-8) and 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB 153) (CAS No. 35065-27-1) in female Harlan Sprague-Dawley rats (gavage studies). Natl. Toxicol. Program Tech. Rep. Ser., 1–258 (2006).
• 9)    Petriello  MC,  Hoffman  JB,  Vsevolozhskaya  O,  Morris  AJ,  Hennig  B. Dioxin-like PCB 126 increases intestinal inflammation and disrupts gut microbiota and metabolic homeostasis. Environ. Pollut., 242, 1022–1032 (2018).
• 10)    Clark  BW,  Matson  CW,  Jung  D,  Di Giulio  RT. AHR2 mediates cardiac teratogenesis of polycyclic aromatic hydrocarbons and PCB-126 in Atlantic killifish (Fundulus heteroclitus). Aquat. Toxicol., 99, 232–240 (2010).
• 11)    Ahmed  RG,  El-Gareib  AW,  Shaker  HM. Gestational 3,3′,4,4′,5-pentachlorobiphenyl (PCB 126) exposure disrupts fetoplacental unit: fetal thyroid-cytokines dysfunction. Life Sci., 192, 213–220 (2018).
• 12)    Liu  H,  Shi  L,  Giesy  JP,  Yu  H. Polychlorinated diphenyl sulfides can induce ROS and genotoxicity via the AhR-CYP1A1 pathway. Chemosphere, 223, 165–170 (2019).
• 13)    Baker  NA,  Shoemaker  R,  English  V,  Larian  N,  Sunkara  M,  Morris  AJ,  Walker  M,  Yiannikouris  F,  Cassis  LA. Effects of Adipocyte Aryl Hydrocarbon Receptor Deficiency on PCB-Induced Disruption of Glucose Homeostasis in Lean and Obese Mice. Environ. Health Perspect., 123, 944–950 (2015).
• 14)    Zhang  W,  Sargis  RM,  Volden  PA,  Carmean  CM,  Sun  XJ,  Brady  MJ. PCB 126 and other dioxin-like PCBs specifically suppress hepatic PEPCK expression via the aryl hydrocarbon receptor. PLoS One, 7, e37103 (2012).
• 15)    Shimada  T,  Inoue  K,  Suzuki  Y,  Kawai  T,  Azuma  E,  Nakajima  T,  Shindo  M,  Kurose  K,  Sugie  A,  Yamagishi  Y,  Fujii-Kuriyama  Y,  Hashimoto  M. Arylhydrocarbon receptor-dependent induction of liver and lung cytochromes P450 1A1, 1A2, and 1B1 by polycyclic aromatic hydrocarbons and polychlorinated biphenyls in genetically engineered C57BL/6J mice. Carcinogenesis, 23, 1199–1207 (2002).
• 16)    Toborek  M,  Barger  SW,  Mattson  MP,  Espandiari  P,  Robertson  LW,  Hennig  B. Exposure to polychlorinated biphenyls causes endothelial cell dysfunction. J. Biochem. Toxicol., 10, 219–226 (1995).
• 17)    Stegeman  JJ,  Hahn  ME,  Weisbrod  R,  Woodin  BR,  Joy  JS,  Najibi  S,  Cohen  RA. Induction of cytochrome P4501A1 by aryl hydrocarbon receptor agonists in porcine aorta endothelial cells in culture and cytochrome P4501A1 activity in intact cells. Mol. Pharmacol., 47, 296–306 (1995).
• 18)    Arzuaga  X,  Wassenberg  D,  Di Giulio  R,  Elskus  A. The chlorinated AHR ligand 3,3′,4,4′,5-pentachlorobiphenyl (PCB126) promotes reactive oxygen species (ROS) production during embryonic development in the killifish (Fundulus heteroclitus). Aquat. Toxicol., 76, 13–23 (2006).
• 19)    Shimizu  K,  Ogawa  F,  Thiele  JJ,  Bae  S,  Sato  S. Lipid peroxidation is enhanced in Yusho victims 35 years after accidental poisoning with polychlorinated biphenyls in Nagasaki, Japan. J. Appl. Toxicol., 27, 195–197 (2007).
• 20)    Diliberto  B. Birnbaum. Role of CYP1A2 in Hepatic Sequestration of Dioxin: Studies Using CYP1A2 Knock-Out Mice1. Biochem. Biophys. Res. Commun., 236, 431–433 (1997).
• 21)    Chen  JJ,  Chen  GS,  Bunce  NJ. Inhibition of CYP 1A2-dependent MROD activity in rat liver microsomes: an explanation of the hepatic sequestration of a limited subset of halogenated aromatic hydrocarbons. Environ. Toxicol., 18, 115–119 (2003).
• 22)    Sipes  IG,  Slocumb  ML,  Chen  HS,  Carter  DE. 2,3,6,2′,3′,6′-hexachlorobiphenyl: distribution, metabolism, and excretion in the dog and the monkey. Toxicol. Appl. Pharmacol., 62, 317–324 (1982).
• 23)    Birnbaum  LS. Distribution and excretion of 2,3,6,2′,3′,6′- and 2,4,5,2′,4′,5′-hexachlorobiphenyl in senescent rats. Toxicol. Appl. Pharmacol., 70, 262–272 (1983).
• 24)    Genuis  SJ,  Beesoon  S,  Birkholz  D. Biomonitoring and Elimination of Perfluorinated Compounds and Polychlorinated Biphenyls through Perspiration: Blood, Urine, and Sweat Study. ISRN Toxicol., 2013, 483832 (2013).
• 25)    Kitamura  K,  Nagahashi  M,  Sunaga  M,  Watanabe  S,  Nagao  M. Balance of Intake and Excretion of 20 Congeners of Polychlorinated Dibenzo-p-dioxin, Polychlorinated Dibenzofuran and Coplanar Polychlorinated Biphenyl in Healthy Japanese Men. J. Health Sci., 47, 145–154 (2001).
• 26)    Takenaka  S,  Takahashi  K. Enhancement of fecal excretion of polychlorinated biphenyls by the addition of rice bran fiber to the diet in rats. Chemosphere, 22, 375–381 (1991).
• 27)    Takenaka  S,  Morita  K,  Tokiwa  H,  Takahashi  K. Effects of rice bran fibre and cholestyramine on the faecal excretion of Kanechlor 600 (PCB) in rats. Xenobiotica, 21, 351–357 (1991).
• 28)    Mochida  Y,  Fukata  H,  Matsuno  Y,  Mori  C. Reduction of dioxins and polychlorinated biphenyls (PCBs) in human body. Fukuoka Igaku Zasshi, 98, 106–113 (2007).
• 29)    Iida  T,  Todaka  T,  Hirakawa  H,  Hori  T,  Tobiishi  K,  Matsueda  T,  Watanabe  S,  Yamada  T. Concentration and distribution of dioxins and related compounds in human tissues. Chemosphere, 67, S263–S271 (2007).
• 30)    Dungkokkruad  P,  Tomita  S,  Hiromori  Y,  Ishida  K,  Matsumaru  D,  Mekada  K,  Nagase  H,  Tanaka  K,  Nakanishi  T. Alginate-coated activated charcoal enhances fecal excretion of 2,3,7,8-tetrachlorodibenzo-p-dioxin in mice, with fewer side effects than uncoated one. J. Toxicol. Sci., 46, 379–389 (2021).
• 31)    Ohta  C,  Haraguchi  K,  Kato  Y,  Endo  T,  Kimura  O,  Koga  N. Distribution and excretion of 2,2′,3,4′,5,5′,6-heptachlorobiphenyl (CB187) and its metabolites in rats and guinea pigs. Chemosphere, 118, 5–11 (2015).
• 32)   Herbst M, United Nations Environment Programme, World Health Organization. Lindane. World Health Organization, Genève, Switzerland, (1991).
• 33)    Abraham  K,  Hille  A,  Ende  M,  Helge  H. Intake and fecal excretion of PCDDs, PCDFs, HCB and PCBs (138, 153, 180) in a breast-fed and a formula-fed infant. Chemosphere, 29, 2279–2286 (1994).
• 34)    Yamasaki  T,  Ishii  T. Studies on the mechanism of action of insecticides. X. Nervous activity as a factor of development of γ-BHC symptoms in the cockroach. Bochu-Kagaku, 19, 106–112 (1954).
• 35)    Kaushik  P,  Kaushik  G. An assessment of structure and toxicity correlation in organochlorine pesticides. J. Hazard. Mater., 143, 102–111 (2007).
• 36)    Thorpe  E,  Walker  AI. The toxicology of dieldrin (HEOD). II. Comparative long-term oral toxicity studies in mice with dieldrin, DDT, phenobarbitone, -BHC and -BHC. Food Cosmet. Toxicol., 11, 433–442 (1973).
• 37)    Nakajima  E,  Shindo  H,  Kurihara  N. Whole Body Autoradiographic Studies on the Distribution of α-, β-and γ-BHC-14C in Mice. Radioisotopes, 19, 532–538 (1970).
• 38)    Birnbaum  LS,  Decad  GM,  Matthews  HB. Disposition and excretion of 2,3,7,8-tetrachlorodibenzofuran in the rat. Toxicol. Appl. Pharmacol., 55, 342–352 (1980).