Comparison between "Yusho" patients and healthy Japanese in contamination level of dioxins and related chemicals and frequency of sister chromatid exchanges

Highly toxic organochlorine chemicals such as polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and coplanar polychlorinated biphenyls (CoPCBs) were determined in the peripheral blood and sebum from the face of 16 "Yusho" patients of about 27 yr after the outbreak of Yusho accident, and 39 healthy Japanese people. The mean total toxic equivalent (TEQ) levels of PCDDs, PCDFs and CoPCBs in the blood were still about seven times higher in Yusho patients than in healthy Japanese at the age of 45 yr and more. The sebum excretion of these chemicals seemed proportional to their blood levels in Yusho patients. These toxic chemicals, however, did not enhance frequencies of sister chromatid exchanges (SCEs) in the control and 7,8-benzoflavone (ANF) treated cultures in Yusho patients. Hence, no significant difference was observed in the mean SCE rates between the Yusho patients and general Japanese people of more than 45 yr of age. In this study, the number of Yusho patients examined is limited, so further large-scale investigations are needed to get more conclusive results concerning the genotoxic potency such as SCE induction.

Effect of dioxins in mother's milk on sister chromatid exchange frequency in infant lymphocytes

Sister chromatid exchange (SCE) frequency which was an index to the synthetic and sharp genetic toxicity was examined using the infant lymphocyte cells around postnatal of 1 year. SCE frequency as the control culture which was treated with the solvent, DMSO, alone (SCEcontrol) was 8.2 +/- 0.9/cell and as cultured with 7,8-benzoflavone (ANF) (SCEANF) was 11.8 +/- 1.4/cell. In addition, the difference of SCEANF and SCEcontrol, namely, delta SCEs became 3.6 +/- 1.3/cell. The concentration of the dioxins in the mother's milk, which had taken by the infants, in the 2-4 month postpartum was 0.95 +/- 0.51 pg-TEQ/g in the male infants, and 0.97 +/- 0.48 pg-TEQ/g in the female ones. The sex difference could not be recognized in contamination levels of the dioxins in mother's milk. The SCE frequency of the infant lymphocytes was examined in order to evaluate the genetic toxicity of the dioxins which had contaminated mother's milk. As the result, either the SCE frequencies or delta SCEs did not show any significant correlation to the dioxins. Therefore, the dioxins were considered not to induce the genetic toxicity such as the SCEs at the present levels of pollution in Japanese mother's milk around postnatal of 1 year.

Effects of donor age and contamination level of dioxins and related chemicals on frequency of sister chromatid exchanges in human lymphocytes cultured in vitro

Frequencies of sister chromatid exchanges (SCEs) of human lymphocytes in control (DMSO treated) and 7,8-benzoflavone (ANF) treated cultures were measured in 39 healthy Japanese people and examined in connection with donor age. Both the control (baseline) and ANF induced SCE rates were significantly enhanced with age and highly positive correlation was observed between them. Therefore, in vivo aging seemed to have some effects on the frequencies of SCEs in human lymphocytes cultured in vitro. Concentrations of PCDDs, PCDFs and Co-PCBs in the blood and sebum of face were determined in the same Japanese subjects. Significantly positive correlation was observed between the blood and sebum in their total TEQ levels. Hence, PCDDs, PCDFs and Co-PCBs, which have been contaminating human bodies, are considered proportionally excreted from the sebum of face or body. Their total TEQ concentrations were also meaningfully increased with donor age in the sebum of face as well as in the blood. Either the baseline or ANF induced SCE frequencies was not enhanced with the total TEQ levels in the blood. Therefore, background levels of their contamination seem not to affect the SCE rates of the lymphocytes in the control and ANF treated cultures.

Effects of contamination level of dioxins and related chemicals on thyroid hormone and immune response systems in patients with "Yusho"

Effects of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and coplanar polychlorinated biphenyls (Co-PCBs) on thyroid hormone and immune response systems were examined in 16 Yusho patients at about 30 years after the outbreak of the Yusho accident. Their toxic equivalent (TEQ) levels in the blood were 27.8-1048.5 pg/g fat with the median level of 222.4 pg/g fat, which was about seven times higher than that of healthy Japanese people. Even at such high blood TEQ concentrations, they seemed not to affect the serum levels of thyroid hormones, thyroid stimulating hormone (TSH), immunoglobulins (A, G and M), autoantibodies (antinuclear antibody, rheumatoid and lupus erythematosus (LE) factors), and lymphocyte subsets in the blood. However, positive rates of rheumatoid factor were considered to increase in higher blood TEQ groups. This investigation was done using rather small number of Yusho patients, so further large-scale investigations are needed to get more conclusive findings concerning their effects on thyroid hormone and immune response systems.

Retrovirus insertion and transcriptional activation of the multidrug-resistance gene in leukemias treated by a chemotherapeutic agent in vivo

To understand the molecular basis for multidrug-resistant (MDR) cancer cells in vivo, this study analyzed molecular changes of the mdr1a gene region in leukemia cells in mice during continuous treatment with vincristine. An inverse insertion of murine leukemia retrovirus (MuLV) into the 5'-flanking region of the mdr1a gene was found. This insertion was concomitantly accompanied by up-regulation of the mdr1a gene and the loss of chemosensitivity. Deletion of long-terminal repeat (LTR) sequences dramatically decreased the mdr1a promoter-driven reporter activity. The MuLV LTR insertion appears to exert its enhancer activity on mdr1a transcription during the appearance of MDR leukemia cells. Two mechanisms were postulated to explain the mdr1a gene activation by retrovirus insertion during in vivo chemotreatment: de novo insertion of MuLV induced by vincristine treatment and selection of a small fraction of pre-existing cells carrying MuLV insertion during vincristine treatment. No rearranged sequence was detected by polymerase chain reaction in parental cells. This result argued for the first mechanism. The randomly altered distribution of MuLV during repetitive chemotreatment might also be consistent with this hypothesis. On the other hand, the retrovirus insertion was detected at the same site of the mdr1a promoter region in 2 independent experiments, which suggests the second mechanism. It should be noted that in vivo chemotreatment using vincristine could generate the mdr1a-overexpressing cells through retrovirus insertion and the enhancer effect of the LTR.

MDR1 gene overexpression and altered degree of methylation at the promoter region in bladder cancer during chemotherapeutic treatment

Overexpression of the multidrug resistance 1 (MDR1) gene is closely associated with the clinical outcome of hematopoietic malignancies, but the alteration of its expression during chemotherapeutic treatment and the precise mechanism underlying MDR1 gene overexpression in solid tumors remains unclear. We determined the expression and degree of methylation at the promoter of the MDR1 gene in bladder cancer. The mRNA levels of the MDR1 gene were found to be markedly enhanced, 3.5- to 5.7-fold higher in bladder cancers after chemotherapeutic treatment than those in untreated primary tumors. The MDR1 gene was overexpressed in recurrent tumors in 89% of patients who showed rerecurrence, whereas overexpression was observed in 25% of the patients without re-recurrence. A statistically significant inverse correlation existed between MDR1 expression and the methylation of 5'CpG sites at the promoter in patients with bladder cancer after chemotherapeutic treatment, with the degree of methylation at several CpG sites, rather than other specific sites, involved in this regulation. Consistent with the increase in MDR1 expression, the frequency of patients with a hypermethylated promoter decreased to 50 and 17% after intravesical and systemic chemotherapy, respectively. Thus, overexpression of the MDR1 gene might be a prognostic marker for intravesical recurrence, whereas methylation of the promoter region negatively regulates MDR1 expression and the appearance of multidrug resistance mediated by P-glycoprotein in bladder cancers.

Alu-associated interstitial deletions and chromosomal re-arrangement in 2 human multidrug-resistant cell lines

Previous studies have shown that gene re-arrangements play a significant role in tumorigenesis. Gene re-arrangements involving the human multidrug resistance-1 (MDR1) gene have been identified as a mechanism for MDR1 over-expression in human malignant cells. In 2 multidrug-resistant human cancer sublines with high levels of MDR1 and P-glycoprotein (MCF7/TX400 and S48-3s/Adr10), hybrid mRNAs containing sequences from MDR1 and an unrelated gene have previously been identified. To characterize and determine the site of the re-arrangements resulting in generation of hybrid mRNAs, we first constructed a lambda phage library extending over a contiguous genomic region of 100 kb and containing the region upstream of MDR1. In MCF7/TX400 cells, homologous recombination was observed involving an Alu repeat 80 kb upstream of the MDR1 gene, with a 79 bp intra-Alu deletion flanked by chi-like sequences at the re-arrangement junction. By contrast, non-homologous recombination was observed in S48-3s/Adr10 cells with Alu repeats near the junction sequence. While the specific features of the breakpoints appear to be different, Alu repeats might be involved in both gene re-arrangements. The gene re-arrangements at or near the Alu sequence should be regarded as potentially involved in the transcriptional activation of human MDR1.

Polychlorinated dibenzo-p-dioxins and related compounds: the blood levels of young Japanese women

We investigated PCDDs and related compounds in the blood of young Japanese women, approximately 20 years of age, who had not yet had children, and discussed how the TEQ level of PCDDs and related compounds in their blood may affect the next generation. Means of total TEQ levels were 0.063 pg/g for whole blood basis and 21 pg/g for lipid basis. TEQ of PCDDs, PCDFs and coplanar PCBs accounted for about 43, 34 and 23% of the total TEQ in the whole blood basis, respectively. In the lipid basis, their values were about 44, 34 and 22%, respectively. Previously, we investigated PCDDs and related compounds levels in mother's breast milk, lymphocyte subpopulation and thyroid function of their children, and found negative correlations between the TEQ level of PCDDs and related compounds and CD4+/CD8+, and/or the TEQ level of PCDDs and related compounds and the T4 level in 36 mothers and children. Of these cases, the average age was approximately 28 years. PCDDs and related compounds may be related to immunopathy, such as atopic dermatitis. The effects of PCDDs and related compounds on babies of young Japanese women are important and must be further evaluated.

Maternal body burden of organochlorine pesticides and dioxins

To investigate the body burden of organochlorine pesticides and dioxins in Japanese women, 125 milk samples were collected from 41 mothers in 1994, 42 in 1995, and 42 in 1996. Of the 125 samples, 82 were from primipara mothers (first delivery) and 43 were from multipara mothers (second or later delivery). By using capillary gas chromatography with electron capture detection, beta-HCH and p,p'-DDE were detected as the major chlorine pesticides in human milk. Average levels of beta-HCH and p,p'-DDE were 475 and 368 ng/g lipid, respectively, in primipara breast milk, 314 and 259 ng/g lipid in multipara breast milk, and 420 and 330 ng/g lipid in total breast milk. Dieldrin, heptachor epoxide, oxychlordane, trans-chlordane, and cis-chlordane were detected at lower average levels of 3, 4, 34, 41, and 5 ng/g lipid, respectively. By using high-resolution gas chromatography with mass spectrometric detection, dioxins were detected in all samples. Average levels of total polychlorinated dibenzo-p-dioxin (PCDD), total polychlorinated dibenzofuran (PCDF), total PCDD + PCDF, total coplanar polychlorinatedbiphenyl (CoPCB), and total dioxin were 10.0, 7.8, 17.7, 9.9, and 27.5 TEQ (toxic equivalent) pg/g lipid, respectively, in primipara breast milk; 7.0, 5.8, 12.8, 7.3, and 20.1 TEQ pg/g lipid in multipara breast milk; and 8.9, 7.1, 16.1, 8.9, and 25.0 TEQ pg/g lipid in total breast milk. In primipara breast milk, significant correlations were found among levels of beta-HCH, p,p'-DDE, total PCDD-TEQ, total PCDF-TEQ, total CoPCB-TEQ, and total TEQ except for less correlation between p,p'-DDE and total PCDF-TEQ. Levels of these analytes also significantly increased depending on mother's age, except for total Co-PCB-TEQ. For the correlation with food habit, the only positive correlation was between total PCDF-TEQs and fish intake.

Induction of sister chromatid exchanges in cultured human lymphocytes with methylsulphonyl PCB congeners

Methylsulphonyl polychlorinated biphenyls (MSF-PCBs) have already contaminated at relatively high concentration in the lungs and blood of Yusho patients and healthy Japanese people. Therefore, we should give due attention to their biological and toxicological effects to man. In this study, in order to evaluate S-dependent genotoxicity of five MSF-PCB congeners, namely, 3-MSF-4,5,3',4'-tetrachlorobiphenyl (TCB), 3-MSF-4,5,2',3'-TCB, 3-MSF-2,5,2',4',5'-pentachlorobiphenyl (PenCB), 4-MSF-2,5,2',3',4'-PenCB and 4-MSF-2,5,2',3',5',6'-hexachlorobiphenyl (HCB), we have examined their effects on the induction of sister chromatid exchanges (SCEs), which has been frequently used to estimate the dose of S-dependent clastogens, in cultured human lymphocytes in the absence or presence of 2,3,4,7,8-pentachlorodibenzofuran (PenCDF), 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or 3,4,5,3',4'-pentachlorobiphenyl (Co-PenCB) and the following results were obtained. 1) 4 x 10(-5)M, 7,8-benzoflavone (ANF) and two of the five MSF-PCB congeners, namely, 3-MSF-2,5,2',4',5'- and 4-MSF-2,5,2',3',4'-PenCB at respective doses of 5.2 and 5.8 ppm, which were about 35,000 times higher than the concentrations in the lungs and adipose tissue of healthy Japanese people, significantly enhanced the frequency of SCEs. 2) In the simultaneous treatment of one of the five MSF-PCB congeners and PenCDF (3.9 ppb), TCDD (1.5 ppb) or Co-PenCB (8.8 ppb), the combination of 3-MSF-4,5,3',4'-TCB (6.8 ppb) or 4-MSF-2,5,2',3',5',6'-HCB and one of the three highly toxic chemicals significantly promoted the formation of SCEs. We have already studied whether these MSF-PCBs are non-S-dependent genotoxic compounds or not and have obtained the results that they seemed not to be or very weak ones. Therefore, based on the results of this and our former studies, the five MSF-PCB congeners examined are considered rather potent S-dependent genotoxic chemicals than non-S-dependent ones.

Polychlorinated dibenzo-p-dioxins and related compounds in breast milk of Japanese primiparas and multiparas

We analyzed polychlorinated dibenzo-p-dioxins and related compounds in the breast milk of primiparas and multiparas, and estimated the levels transferred to newborns by breast milk in Western Japan. 2,3,7,8-TeCDD equivalents (TEQ) of the chemicals in primiparas decreased slightly from 1994 to 1996. In particular, decreases of the TEQs of total PCDDs and total coplanar PCBs were higher than that of total PCDFs. In 2,3,7,8-TeCDD, 1,2,3,7,8-PeCDD, 1,2,3,6,7,8-HxCDD, 1,2,3,7,8,9-HxCDD, 2,3,4,7,8-PeCDF, 1,2,3,6,7,8-HxCDF, 3,3',4,4',5-PeCB and 3,3',4,4',5,5'-HxCB concentrations, those in the breast milk of multiparas were significantly lower than those in the breast milk of primiparas (p < 0.05, lipid basis). Based on the assumption that newborns ingest 120 g of breast milk per kg body weight per day, the amounts converted to TEQ values were 121 pg/kg/day (primiparas) and 97.2 pg/kg/day (multiparas).

Polychlorinated dibenzo-p-dioxins and related compounds: correlations of levels in human tissues and in blood

We investigated PCDDs and related compounds levels in human tissue and blood obtained from the general population, and the correlation factor was calculated from the findings. None of the congeners in brain, muscle and lung were correlated except for 2,3,7,8-tetrachlorodibenzo-p-dioxin and octachlorodibenzo-p-dioxin in the brain (p < 0.05). In other tissues, all congeners had relatively good correlations to those in blood (r > 0.707). These congeners detected in blood were at high concentrations in the environment and human body. Therefore, we concluded that these congener levels in the blood might be useful for estimating these congener levels in human tissue.

Hypomethylation status of CpG sites at the promoter region and overexpression of the human MDR1 gene in acute myeloid leukemias

Selection of human cells for resistance to vincristine or doxorubicin often induces overexpression of the multidrug resistance 1 gene (MDR1), which encodes the cell surface P-glycoprotein, as a result of gene amplification or transcriptional activation. Moreover, overexpression of the MDR1 gene has been shown to be associated closely with clinical outcome in various hematological malignancies, including acute myeloid leukemia (AML). However, the precise mechanism underlying overexpression of the MDR1 gene during acquisition of drug resistance remains unclear. We recently described an inverse correlation between the methylation status of CpG sites at the promoter region and expression of the MDR1 gene in malignant cell lines. In this study, we expanded this analysis to 42 clinical AML samples. We adapted a quantitative reverse transcription-polymerase chain reaction (RT-PCR) assay for gene expression and a quantitative PCR after digestion by Hpa II for methylation status of the MDR1 gene. We observed a statistically significant inverse correlation between methylation and MDR1 expression in clinical samples. The hypomethylation status of the MDR1 promoter region might be a necessary condition for MDR1 gene overexpression and establishment of P-glycoprotein-mediated multidrug resistance in AML patients.

Postnatal exposure to chlorinated dioxins and related chemicals on lymphocyte subsets in Japanese breast-fed infants

Effects of postnatal exposure to polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and coplanar polychlorinated biphenyls (Co-PCBs) on lymphocyte subpopulations were investigated in the peripheral blood of 36 breast-fed Japanese babies. As a result, estimated total intakes of these chemicals in toxic equivalent quantity (TEQ) converted into 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) equivalents from the breast milk positively and negatively correlated with the respective percentages of CD4+ and CD8+ lymphocytes in the blood of breast-fed babies. Consequently, the ratios of CD4+ to CD8+ T cells showed significant increasing tendency with the estimated total TEQ intakes. Therefore, our study suggests that exposure to background levels of the highly toxic organochlorine compounds through the breast milk influences the human neonatal immune system.

Postnatal exposure to chlorinated dioxins and related chemicals on thyroid hormone status in Japanese breast-fed infants

Effects of postnatal exposure to polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and coplanar polychlorinated biphenyls (Co-PCBs) on thyroid hormone status were studied in the peripheral blood of 36 breast-fed Japanese infants. Estimated total intakes of these chemicals in toxic equivalent quantity (TEQ) converted into 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) from the breast milk significantly and negatively correlated with the levels of triiodothyronine (T3) and thyroxine (T4) in the blood of breast-fed babies. Therefore, exposure to background levels of the highly toxic organochlorine chemicals through the breast milk may cause some effects on thyroid hormone status in Japanese infants.

Induction of micronuclei in cultured human lymphocytes with the mixture of highly toxic organochlorine compounds retained in human body

In this study, we investigated the effect of mixture of the organochlorine compounds, which very resembled their contamination profile of healthy Japanese people in its composition, on the induction of micronuclei in human whole-blood cultures in order to clarify their genotoxicity as a whole. The following results were obtained. Regardless of the presence or absence of 7, 8-benzoflavone (ANF) in the blood culture system, we observed a fairly good dose-response relationship between the concentration of the mixture and the induction of micronuclei. In particular, we found that 50% effective concentration of the mixture of the organochlorine chemicals was considered only about 7 times greater level over the average concentration in the healthy people, namely 70ppt as 2, 3, 7, 8-TCDD, in the absence of ANF and about 5 times more than that in the presence of ANF. Based on these results, the mixture was regarded as extremely genotoxic. Our human bodies, however, have already been contaminated with a variety of chemicals including PCDDs, PCDFs and Co-PCBs and accordingly one of the most important problems to be solved is a further comprehensive genotoxicity and health consequences due to these chemicals to the descendants.

Effect of 2, 3, 4, 7, 8-pentachlorodibenzofuran and its analogues on induction of sister chromatid exchanges in cultured human lymphocytes

We have been already contaminated with various chemicals including highly toxic organochlorine compounds such as 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD), 2, 3, 4, 7, 8-pentachlorodibenzofuran (PenCDF) and 3, 4, 5, 3', 4'-pentachlorobiphenyl (Co-PenCB). In this study, in order to evaluate the genotoxicity of the three chemicals, we have examined their effects on the induction of sister chromatid exchanges (SCEs), which has been frequently utilized as an indicator of biological and genetic damage due to exposure to carcinogens or mutagens, in cultured human lymphocytes in the absence or presence of 7, 8-benzoflavone (ANF) and the following results were obtained. 1) TCDD, PenCDF and Co-PenCB significantly increased the frequency of SCEs with almost the same dose-dependent manner in terms of the concentration of TCDD toxic equivalent. 2) 8 x 10(-5) MANF significantly enhanced the frequency of SCEs and the simultaneous treatment of ANF and either of TCDD, PenCDF or Co-PenCB seemed to exert an additive effect as SCEs inducer. 3) TCDD, PenCDF and Co-PenCB were considered to be very potent inducers of SCEs, because their 50% effective concentration in SCEs enhancement were only 5 to 10 times higher than the level of the adipose tissue in healthy Japanese, namely, 70ppt as TCDD. Consequently, the respective TCDD toxic equivalency factors of 0.5 and 0.2 for PenCDF and Co-PenCB seemed to be reasonable so far as the induction of SCEs was employed as an indicator of the genotoxic potency.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of five methylsulphonyl PCB congeners on frequency of micronucleated cells in cultured human lymphocytes by cytokinesis block method

The lungs and blood of Yusho patients and healthy Japanese people have already been contaminated with methylsulphonyl polychlorinated biphenyls (MSF-PCBs) at relatively high concentration. Therefore, we should give due attention to their biological and toxicological effects to man. In this study, in order to mainly evaluate non-S-dependent genotoxicity of five MSF-PCB congeners, namely, 3-MSF-4, 5, 3', 4'-tetrachlorobiphenyl (TCB), 3-MSF-4, 5, 2', 3'-TCB, 3-MSF-2, 5, 2', 4', 5'-pentachlorobiphenyl (PenCB), 4-MSF-2, 5, 2', 3', 4'-PenCB and 4-MSF-2, 5, 2', 3', 5', 6'-hexachlorobiphenyl (HCB). We have examined their effects on the induction of micronucleated cells, which has been frequently used to estimate the dose of ionizing radiation and truly radiomimetic, non-S-dependent, clastogens, in cultured human lymphocytes in the absence or presence of 2, 3, 4, 7, 8-pentachlorodibenzofuran (PenCDF), 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD) or 3, 4, 5, 3', 4'-pentachlorobiphenyl (Co-PenCB). The following results were obtained. 1) 4 x 10(-5) M7, 8-benzoflavone (ANF) significantly enhanced the frequency of micronucleated cells and all of the five MSF-PCB congeners failed to induce the formation of micronucleated cells at doses of 5.2 to 9.6 ppm, which were about 35,000 times higher than the concentrations in the lungs and adipose tissue of healthy Japanese people.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of highly toxic organochlorine compounds retained in human body on induction of sister chromatid exchanges in cultured human lymphocytes

In this study, we investigated the effect of mixture of the organochlorine compounds, which very resembled their contamination of healthy Japanese people in its composition, on the induction of sister chromatid exchanges (SCEs) in human whole-blood cultures in order to clarify their genotoxicity as a whole. The following results were obtained. Regardless of the presence or absence of 7,8-benzoflavone (ANF) in the blood culture system, we could observe a fairly good dose-response relationship between the concentration of the mixture of organochlorine compounds and the induction of SCEs/cell. In particular, we found that 50% effective concentration of the mixture of the organochlorine compounds was considered to be only about 3 times greater level over the average concentration in the healthy people, namely 70ppt as 2,3,7,8-TCDD, in the absence of ANF and about 8 times more than that in the presence of ANF.

Effects of methylsulphonyl polychlorinated biphenyl homologues and 7,8-benzoflavone on aryl hydrocarbon hydroxylase activity

First, we investigated the effects of eleven methylsulphonyl polychlorinated biphenyl (MSF-PCB) homologues at 1.5 micrograms/ml and 7,8-benzoflavone (ANF) at 1.4 micrograms/ml on 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, 15 ng/ml)-induced aryl hydrocarbon hydroxylase (AHH) activity of cultured human lymphoblastoid cells and the following results were obtained. 1) The relative AHH activity (TCDD-induced AHH activity treated with each of the MSF-PCB compounds or ANF/the enzyme activity treated with acetone, %) of the ANF-treated culture was the smallest value (about 9%). 2) Among MSF-PCB homologues, 3-MSF-4,5,3',4'- and 4-MSF-3,5,3',4'-tetrachlorobiphenyls (TCBs) showed the highest inhibition and their relative enzyme activities were about 20%. 3) In the rest of MSF-PCB compounds, the relative AHH activities were as follows: 4-MSF-3,5,3',4',5'-pentachlorobiphenyl (PenCB); 37%, 3-MSF-4,5,2',3',4'-PenCB; 50%, 3-MSF-4,5,2',3'-TCB, 3-MSF-4,5,2',3',4',5'-hexachlorobiphenyl and 3-MSF-4,5,6,2',3',4',5'-heptachlorobiphenyl; 60 to 64%, 4-MSF-2,5,2',3',4'-PenCB; 77%, 3-MSF-2,5,3',4'-TCB; 88%, 4-MSF-2,5,2',5'-TCB; 93% and 3-MSF-4,5,3',4',5'-PenCB rather enhanced the TCDD-induced enzyme activity. Second, we prepared the hepatic microsomes of BALB/c (Ah responsive) and AKR/J (Ah nonresponsive) strains of mice after the treatment of olive oil (as control), 3-methylcholanthrene (MC, 42 mg/kg, once) and TCDD (20 micrograms/kg, 6 times, once every other week) in order to examine the effects of 3-MSF-4,5,3',4'-TCB (1.5 to 45 micrograms/ml) and ANF (1.4 to 42 micrograms/ml) on the respective hepatic microsomal AHH activities.(ABSTRACT TRUNCATED AT 250 WORDS)

[Concentration of PCDDs, PCDFs and coplanar PCBs in breast milk of Yusho patients and normal subjects]

Levels of PCDDs, PCDFs and coplanar PCBs were measured in human breast milk obtained from two Yusho patients and nine healthy subjects. The concentrations of PCDDs, PCDFs and coplanar PCBs in the breast milk of respective Yusho patients were 18.2 and 28.9, 168.8 and 418.3, and 23.8 and 55.1 pg Toxic Equivalents (TEQs)/g fat, respectively, and their mean concentrations in normal controls were 8.2, 5.1 and 21.8 pg TEQ/g fat, respectively. The results also indicated that there was a significant difference between Yusho patients and normal subjects in the concentrations of certain isomers of PCDDs, PCDFs and coplanar PCBs in the breast milk. For example, the levels of 1, 2, 3, 6, 7, 8-HxCDD were 4 and 8 times higher than the mean concentration in the normal subjects, and 2, 3, 4, 7, 8-PeCDF, 1, 2, 3, 4, 7, 8-HxCDF and 1, 2, 3, 6, 7, 8-HxCDF, so-called 'Yusho isomers' were 15 to 98 times higher than those in the normal subjects. Daily intakes of TEQ values were estimated to be 506 and 2200 pg TEQs/kg/day for breast-feeding babies of Yusho patients, and to be from 97 to 197 pg TEQs/kg/day for healthy subjects. These TEQ values were much greater than the ADI of 1-10 pg/kg/day, therefore, we should give due attention to the possible health effects due to PCDDs, PCDFs and coplanar PCBs in the breast milk of healthy mothers, as well as Yusho mothers.

Frequency of micronuclei induced in cultured lymphocytes by highly toxic organochlorine congeners

Our human bodies have already been contaminated with various chemicals including highly toxic organochlorine compounds such as 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD), 2, 3, 4, 7, 8-pentachlorodibenzofuran (PenCDF) and 3, 4, 5, 3', 4'-pentachlorobiphenyl (PenCB). In this study, in order to evaluate the genotoxicity of these three chemicals, we examined their effects on the induction of micronuclei, which has frequently been utilized as indicator of biological and genetic damage due to exposure to carcinogens or mutagens, in cultured human lymphocytes in the absence or presence of alpha-naphthoflavone (ANF) and the following results were obtained. 1)4 x 10(-5) M ANF alone significantly enhanced the frequency of micronuclei and the combination of ANF and either of TCDD, PenCDF or PenCB seemed to be additive as micronuclei inducers. 2) TCDD, PenCDF and PenCB significantly increased the frequency of micronuclei with almost the same dose-dependent manner in terms of the concentration of TCDD toxic equivalent. 3) TCDD, PenCDF and PenCB were considered to be very potent inducers of micronuclei, because their values of 50% effective concentration in micronuclei enhancement were around only 10 times higher concentration than that in healthy people, namely, 70ppt as TCDD. Consequently, the respective TCDD toxic equivalency factors of 0.5 and 0.2 for PenCDF and PenCB seemed to be reasonable so far as the induction of micronuclei was employed as an indicator of their genotoxic potency.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of 3-methylsulphonyl-4,5,3',4',-tetrachlorobiphenyl and 7,8-benzoflavone on aryl hydrocarbon hydroxylase activities of murine hepatic microsomes prepared from inbred strains with different Ah responsiveness

In this work, we employed three Ah nonresponsive strains of mice, AKR, DBA and DDD, and three Ah responsive ones, C57, BALB and C3H, and prepared hepatic microsomes after the treatment of 3-methylcholanthrene (MC; 42 mg/kg, once) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; 20 micrograms/kg, 6 times) in order to investigate the effect of 3-methylsulphonyl-4,5,3',4'-tetrachlorobiphenyl (3-MSF-4,5,3',4'-TCB; 1.5-45 micrograms/ml) and 7,8-benzoflavone (ANF; 1.4-42 micrograms/ml) on the hepatic microsomal AHH activities and the following results were obtained. 1. In the Ah nonresponsive strains of mice, 70 and 20% of the induced AHH activities with MC and TCDD, respectively, were attributable to the basal control enzyme activity and in the Ah responsive ones, only 4.2 and 1.4% of the induced activities with the two chemicals to the untreated control one, respectively. 2. 3-MSF-4,5,3',4'-TCB and ANF enhanced or reduced the enzyme activity depending on both their concentrations and kinds of microsomes employed, namely, control-, MC- and TCDD-microsomes. ANF showed higher potency for both the activation and inhibition of the AHH activity than 3-MSF-4,5,3',4'-TCB. 3. The effects of 3-MSF-4,5,3',4'-TCB and ANF on the enzyme activity of the MC treated Ah nonresponsive mice and those of the untreated control Ah responsive animals were quite similar and their effects on the AHH activity of the TCDD treated Ah nonresponsive strains were also almost the same as those of the MC or TCDD treated Ah responsive ones.(ABSTRACT TRUNCATED AT 250 WORDS)

An improved method for the detection of differential survival between normal and xeroderma pigmentosum lymphoblastoid cell lines in culture with 4-nitroquinoline-1-oxide

The effects of the UV-mimetic chemical 4-nitroquinoline-1-oxide (4-NQO) upon cell lines heterozygous or homozygous for the recessive mutant xeroderma pigmentosum (XP) were investigated. Human lymphoblastoid cell lines, which were established from 4 XP homozygote patients (XPL15, XPL17, XPL19 and XPL20). 2 XP heterozygote individuals (XPPL17 and XPML17) and 58 normal individuals, were cultured in the presence of 4-NQO at doses of 0, 2, 4 and 8 x 10(-6) M. Then the total cell number was counted and the viability of the cells was measured by the dye exclusion method using trypan blue and a newly devised fluorometric method with fluorescein diacetate. Results showed that 4-NQO affected, in increasing order of impairment, the cell lines: normal less than XP heterozygote less than XP homozygote.

[The effect of organochlorine compounds on the induction of sister chromatid exchanges in cultured human lymphocytes]

In this study, first, we investigated the effect of 7,8-benzoflavone (ANF), mitomycin C (MMC), a well-known genotoxic compound, and ANF plus MMC on the induction of sister chromatid exchanges (SCEs) in human whole-blood cultures. Second, we examined the effect of mixture of organochlorine compounds, which very resembled their contamination of healthy people in its composition, on the induction of SCEs in the same blood culture system in order to clarify their genotoxicity as a whole. The following results were obtained. 1. ANF and MMC significantly enhanced the number of SCEs/cell at the concentrations of 4 x 10(-5) M and 10(-8)M, respectively. When both of the compounds were simultaneously added in the blood cultures, their effects on the induction of SCEs seemed to be additive. 2. Without ANF in the blood culture system, namely, an usual system of the SCEs experiment, we could not find a dose-response relationship between the concentration of the mixture of organochlorine compounds and the induction of SCEs/cell. With ANF, however, we observed a fairly good dose-response relationship between them. 3. In the whole-blood culture system with ANF, we found significantly great number of SCEs/cell at the level of twenty times higher concentration of the organochlorine compounds than the ordinary level. According to the results described above and of our other studies, 50% effective concentration (EC50, about 2 SCEs/cell higher than control SCEs/cell) of the mixture was considered to be about 5 times greater level over the general one.(ABSTRACT TRUNCATED AT 250 WORDS)

[Coplanar PCBs, PCDFs and PCDDs in the subcutaneous adipose tissue of Yusho patients and normal controls]

3,4,3',4'-tetrachlorobiphenyl (T4CB), 3,4,5,3',4'-pentachlorobiphenyl (P5CB) and 3,4,5,3',4',5'-hexachlorobiphenyl (H6CB) [Co-PCBs] in the subcutaneous adipose tissue of seven Yusho patients and eight normal controls were determined to assess the contribution in the risk caused by the Yusho causual agents (PCBs, PCDFs, PCDDs and Co-PCBs) by using high resolution gas chromatography/high resolution mass spectrometry in selected ion monitoring mode. 3,4,3',4'-T4CB, 3,4,5,3',4'-P5CB and 3,4,5,3',4',5'-H6CB were detected in the subcutaneous adipose tissue of the Yusho patients at the levels, of 6 to 29 ppt, of 32 to 130 ppt and of 160 to 1,140 ppt, respectively. The TCDD-Eq (Equivalents) value calculated by TCDD-TEfs (Toxic Equivalent factors) was from 8 to 30 ppt. On the other hand, 3,4,3',4'-T4CB, 3,4,5,3',4'-P5CB and 3,4,5,3',4',5'-H6CB were detected in the subcutaneous adipose tissue of normal controls at the levels, of 3 to 9 ppt, of 41 to 280 ppt and of 47 to 200 ppt, respectively. The TCDD-Eq value calculated by TCDD-TEfs was from 9 to 57 ppt. In the Yusho patients, the average TCDD-Eq value calculated by TCDD-TEfs of the residual Co-PCBs, PCDFs and PCDDs was 17, 491 and 24 ppt, respectively. Therefore, we concluded that the typical symptoms for the Yusho patients are caused mostly by PCDFs.

Effects of 3-methylsulphonyl-4,5,3',4'-tetrachlorobiphenyl and 7,8-benzoflavone on aryl hydrocarbon hydroxylase activity in Ah responsive and Ah nonresponsive strains of mice

In general, C57BL/6NQdj (C57) and DBA/2JCrj (DBA) strains of mice are considered to be the aryl hydrocarbon (Ah) responsive and Ah nonresponsive strains of mice, respectively, which are determined by whether the hepatic aryl hydrocarbon hydroxylase (AHH) activity is enhanced (Ah responsive) or not (Ah nonresponsive) after the treatment of 3-methylcholanthrene (MC). In this study, first, we examined that the Ah responsiveness was systemically regulated in the lungs and kidneys as well as in the liver and observed its systemic control in these three organs in the two strains of mice. Then, we prepared the hepatic microsomes of the two strains of mice after the treatment of MC (42 mg/kg, once), 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, 20 micrograms/kg, 6 times) and 2,3,4,7,8-pentachlorodibenzofuran (PenCDF 60 micrograms/kg, 6 times) in order to investigate the effects of 3-methylsulphonyl-4,5,3',4'-tetrachlorobiphenyl (3-MSF-TCB, 1.5-45 micrograms/ml) and 7,8-benzoflavone (ANF, 1.4-42 micrograms/ml) on the respective hepatic microsomal AHH activities and the following results were obtained. 1. As compared with the control enzyme activity, TCDD-induced AHH activity was the highest, PenCDF-induced one the second and MC-induced the lowest in both strains of mice. The inductions of the enzyme activity by these chemicals were much more remarkable in the Ah responsive C57 strain than those in the Ah nonresponsive DBA strain. 2. 3-MSF-TCB and ANF enhanced or reduced the enzyme activity depending on both their concentrations and kinds of microsomes, namely, those prepared from untreated control mice and mice treated with MC, TCDD or PenCDF.(ABSTRACT TRUNCATED AT 250 WORDS)

Aryl hydrocarbon hydroxylase activity levels in the hepatic microsomal fraction from MC- or TCDD-treated mice: a comparison between aromatic hydrocarbon responsive and non-responsive strains

The effects of in vivo administration of polycyclic aromatic hydrocarbons on the levels of aryl hydrocarbon hydroxylase (AHH) activity in aromatic hydrocarbon (Ah) responsive and non-responsive strains of mice were studied using the hepatic microsomal fraction. Injection of 3-methylcholanthrene (MC; 42 mg/kg body wt.) or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; 120 micrograms/kg body wt.) into both strains produced marked enhancement of AHH activity except for MC treatment of Ah non-responsive strains. Addition of 7,8-benzoflavone (BNF) to the microsomal AHH assay mixture prepared from mice previously injected with vehicle (olive oil) alone caused an increase in activity when the mice were responsive, while BNF lowered the activity in non-responsive strains. With regard to MC-injected mice, BNF and 3-methyl-sulphonyl-4,5,3',4'-tetrachlorobiphenyl (3-MSF-TCB) decreased microsomal AHH activity in Ah-responsive mice, whereas these drugs enhanced the activity in Ah-non-responsive strains. 3-MSF-TCB also had inhibitory potency on AHH activity, but the mechanism of inhibition seems to be somewhat different from that of BNF. It may also suggest that cytochrome P-450 isozymes inhibited by BNF are different from those inhibited by 3-MSF-TCB.

[Effects of 3-methylsulphonyl-4,5,3',4-tetrachlorobiphenyl and 7,8-benzoflavone on aryl hydrocarbon hydroxylase activity]

First, we examined the effects of 3-methylsulphonyl-4,5,3',4',-tetrachlorobiphenyl (3-MSF-TCB, 1.5 ppm) and 7,8-benzoflavone (ANF, 1.4 ppm) on aryl hydrocarbon hydroxylase (AHH) activity in cultured human lymphoblastoid cells and we have obtained the following results: (1) 3-MSF-TCB preferentially inhibited the enzyme activity induced by 2,3,4,7,8-pentachlorodibenzofuran (PenCDF) or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and slightly stimulated the enzyme activity induced by 3-methylcholanthrene (MC). (2) ANF reduced well the AHH activities induced by all the three enzyme inducers and more strongly inhibited the PenCDF- or TCDD-induced enzyme activity (about 89%). (3) About 64 and 76% of basal (uninduced) AHH activity was lowered by 3-MSF-TCB and ANF, respectively. Second, we investigated the effect of 3-MSF-TCB (1.5-45 ppm) and ANF (1.4-42 ppm) on AHH activity of hepatic microsomes from the Ah nonresponsive (DDD) and responsive (C3H) strains of mice and we have got the following results: (1) 3-MSF-TCB and ANF enhanced or reduced the enzyme activity depending on both their concentrations and kinds of microsomes, namely, those prepared from untreated mice (control-microsomes) and mice treated with MC (MC-microsomes) or TCDD (TCDD-microsomes). (2) ANF showed higher potency for both the enhancement and the inhibition of the enzyme activity than 3-MSF-TCB. (3) The AHH activity of TCDD-microsomes seemed to be more greatly reduced with either 3-MSF-TCB or ANF than that of MC-microsomes. (4) The effects of 3-MSF-TCB and ANF on the enzyme activity of MC-microsomes of DDD mice and of control-microsomes of C3H mice.

[AHH activity and life environmental factors]

To investigate life environmental factors which affect aryl hydrocarbon hydroxylase (AHH) activity, basal and 3-methylcholanthrene(3-MC)-induced AHH activities were determined by the formation of 3-hydroxybenzo(a)pyrene in cultured lymphocytes obtained from 111 healthy male subjects who lived in Fukuoka Prefecture, Japan. Fold induction (3-MC-induced/basal) was calculated. Relationship between the absolute activities and the fold induction of AHH and life environmental factors was statistically examined. Study of simple correlation indicated the following: Basal AHH activity was positively correlated with age and habitual intake of drugs. Induced AHH activity was positively correlated with coffee intake, smoking and habitual intake of drugs. Fold induction was positively correlated with coffee intake and smoking, and negatively with age. Using multiple regression analysis, habitual intake of drugs showed positive relation to both basal and induced enzyme activity, and age showed positive relation to the basal activity and negative relation to the fold induction.

PCB and PCDF congeners in the blood and tissues of yusho and yu-cheng patients

Polychlorinated biphenyl (PCB) poisonings occurred in western Japan, where it is called yusho, in 1968, and in central Taiwan, where it is called yu-cheng, in 1979. The average concentrations of PCBs in the adipose tissue, liver and blood of yusho patients and in the blood of yu-cheng patients were 1.9 ppm, 0.08 ppm, 6.7 ppb and 99 ppb, respectively. Seven PCB congeners, such as 2,4,5,3',4'-pentachloro-, 2,3,4,3',4'-pentachloro-, 2,4,5,2',4',5'-hexachloro-, 2,3,4,2',4',5'-hexachloro-, 2,3,4,5,3',4'-hexachloro-, 2,3,4,5,2',4',5'-heptachloro- and 2,3,4,5,2',3',4'-heptachloro biphenyls were identified in the blood and tissues of patients with yusho and yu-cheng and controls. The concentration of 2,3,4,5,3',4'-hexachlorobiphenyl was comparatively higher in the patients than in controls. The concentrations of polychlorinated dibenzofurans (PCDFs) in the adipose tissue and liver of yusho patients were 6 to 13 ppb and 3 to 25 ppb, respectively, while no PCDFs were detected in the controls. Major PCDF congeners identified in the tissues and blood of yusho and yu-cheng patients were the 2,3,6,8-tetrachloro-, 2,3,7,8-tetrachloro-, 1,2,4,7,8-pentachloro-, 2,3,4,7,8-pentachloro- and 1,2,3,4,7,8-hexachlorodibenzofurans (DFs), of which the 2,3,4,7,8-pentachloro compound was predominant. The concentrations of methylthio-PCB in the liver, lung and adipose tissue of yusho patients were 0.1 to 0.5, 0.2 to 1.4 and 0.5 to 1.0 ppb, respectively, and those of methysulfone PCBs were 0.3 to 0.7, 1.0 to 2.5 and 0.7 to 1.0 ppb, respectively. Some of the major peaks of the PCB methylthio and methylsulfone derivatives were identical in gas chromatographic retention times with those of 4-methylthio- and 4-methylsulfone-2,5,2',5'-tetrachlorobiphenyl PCDFs, especially 2,3,4,7,8-pentachloro DF, appear to be mainly responsible in the poisonings.

Genetically mediated induction of aryl hydrocarbon hydroxylase activity in mice by polychlorinated dibenzofuran isomers and 2,3,7,8-tetrachlorodibenzo-p-dioxin

Hepatic aryl hydrocarbon hydroxylase (AHH)-inducing potency of toxic polychlorinated aromatic hydrocarbons such as polychlorinated dibenzofurans (PCDFs), 3,4,5,3',4',5'-hexachlorobiphenyl (HCB) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was studied in four inbred strains of mice with different phenotypes of Ah locus, i.e., AHH-responsive strains: C57BL/6N and AKR/Ms Qdj, and AHH-nonresponsive strains: DBA/2Cr Slc and Qdj; DDD. Eight individual PCDF isomers or TCDD were administered IP in doses of 30 micrograms/kg; HCB was given in a dose of 120 micrograms/kg. In AHH-nonresponsive strains of mice, only TCDD significantly induced hepatic AHH activity, while in AHH-responsive strains, 2,3,7,8-tetrachlorodibenzofuran(2,3,7,8-TCDF), 1,2,3,7,8-pentachlorodibenzofuran(1,2,3,7,8-PCDF), 2,3,4,7,8-pentachlorodibenzofuran(2,3,4,7,8-PCDF), and TCDD significantly enhanced the enzyme activity, and the induced AHH activities with the three PCDF isomers were about 30-65% of those of TCDD. These results indicate that AHH responsiveness in mice segregates with the induction of AHH activity by PCDF isomers and may also segregate with the toxic potency of the isomers; i.e., toxic potencies of 2,3,7,8-TCDF, 1,2,3,7,8-PCDF, and 2,3,4,7,8-PCDF in AHH-responsive strains of mice may be much greater than those in AHH-nonresponsive strains of mice. Taking into account both the potent AHH inducibility and the high bioaccumulation of 2,3,7,8-TCDF, 1,2,3,7,8-PCDF, and 2,3,4,7,8-PCDF, these three PCDF isomers should be given greater attention with regard to environmental contamination.

Genetically mediated induction of aryl hydrocarbon hydroxylase activity in human lymphoblastoid cells by polychlorinated dibenzofuran isomers and 2,3,7,8-tetrachlorodibenzo-p-dioxin

Aryl hydrocarbon hydroxylase(AHH)-inducing potency of toxic polychlorinated aromatic hydrocarbons such as polychlorinated dibenzofuran (PCDF) isomers, 3,4,5,3',4',5'-hexachlorobiphenyl (HCB) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was investigated in human lymphoblastoid cell lines with different AHH inducibility for 3-methylcholanthrene (3-MC) obtained from healthy subjects. Each of the cell lines was treated with eight individual PCDF isomers, TCDD, and HCB at doses of 1.9-15 ng/ml of culture medium, 1.9-7.5 ng/ml and 95 ng/ml, respectively. Lymphoblastoid cell lines were arbitrarily classified into three groups based on their AHH inducibilities with 3-MC (2.5 microM); low (3-MC/control = I less than 3), middle (3 less than or equal to I less than 6) and high (I greater than or equal to 6). Degrees of the enzyme inducibilities of the organochlorine compounds proportionally increased with those for 3-MC. AHH inducibilities with 2,3,4,7,8-pentachlorodibenzofuran(2,3,4,7,8-PCDF), 1,2,3,4,6,7-hexachlorodibenzofuran(1,2,3,4,6,7-HCDF) and 1,2,3,4,7,8-hexachlorodibenzofuran(1,2,3,4,7,8-HCDF) were comparable to those of TCDD at doses of 7.5 ng/ml, and about twice as high as those of 2,3,7,8-tetrachlorodibenzofuran (TCDF), at the same dose, HCB, at a dose of 95 ng/ml, did not induce enzyme activity. The experimental evidence indicated that AHH inducibility by the organochlorine compounds reflected the genetic susceptibility of the cells to the phenomenon of induction, and PCDF isomers found at relatively high concentrations in tissues of mammals exerted the highest values of AHH induction.

A comparative study of polychlorinated dibenzofurans, polychlorinated biphenyls and 2,3,7,8-tetrachlorodibenzo-p-dioxin on aryl hydrocarbon hydroxylase inducing potency in rats

The aryl hydrocarbon hydroxylase (AHH) inducing potency of toxic chlorinated aromatic hydrocarbons such as polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was studied in the young male Wistar rats. Alternatively, a technical PCDF mixture, 15 individual PCDF isomers or TCDD were administered i.p. in doses of 5 micrograms/kg; a PCB mixture was given in a dose of 50 mg/kg. The order of AHH inducing ability was TCDD greater than PCDFs much greater than PCBs in kidney, lung, and liver. In the prostate, thymus, and spleen, only TCDD enhanced the AHH activity. The AHH inducibility in the lung and liver, induced by 15 pure PCDF isomers with varying chlorine substitutions was also examined. Only 2,3,7,8-tetrachlorodibenzofuran (2,3,7,8-tetra-CDF) and 2,3,4,7,8-pentachlorodibenzofurans (2,3,4,7,8-penta-CDF) significantly induced the hepatic AHH activity (4- and 2-fold, respectively), while eight PCDF isomers, including these two, significantly enhanced the pulmonary AHH activity (6- to 30-fold). Taking into account both the potent AHH inducibility and the high bioaccumulation of these compounds, 2,3,7,8-tetra- and 2,3,4,7,8-penta-CDF should be given due attention with regard to environmental-related factors and the possibility of involvement in the etiology of "yusho" disease.