Polychlorinated Biphenyls In Adipose Tissue Research Articles

Accumulation and decontamination kinetics of PCBs and PCDD/Fs from grass silage and soil in a transgenerational cow-calf setting

Polychlorinated biphenyls (PCBs) and dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) are bioaccumulative pollutants that endanger bovine food safety. Bioaccumulation depends, among others, on the physiological dynamics of the cow's reproductive cycle. However, recent studies have focused only on near steady-state situations. Thus, the effects of animal physiology on PCB + PCDD/F transfer from grass silage and soil to cows' blood, adipose tissue, and milk and subsequently to suckling calves during gestation and lactation were investigated. In the exposed group, nine cows ate a grass silage/contaminated soil mixture (6.6 ± 0.8 μg iPCBs and 2.6 ± 0.4 ng dlPCB + PCDD/F TEQ kgDM−1) for 109 days prepartum until 288 days in milk (DIM). Four of these cows underwent decontamination after DIM164, receiving the same clean grass silage as the four control cows during the experiment. Calves were fed the milk of their respective mothers. In the exposed group, transgenerational bioaccumulation occurred until DIM164, with calf blood and adipose tissue PCB + PCDD/F concentrations reaching levels twice as high as those in their respective mothers. Transfer rates from oral intake to milk ranged from 0.1 up to 42%, depending on pollutant congener, dietary treatment, and reproductive parity of the cow. Congener and parity also influenced the decontamination half-lives of milk. In decontaminated calves, declines in adipose tissue PCB + PCDD/F concentrations coincided with increases in body fat mass. Therefore, it is essential to know the physiological characteristics of cattle, exposure dose and duration, and physicochemical compound properties to perform reliable transfer assessments.

Associations between functional polychlorinated biphenyls in adipose tissues and prognostic biomarkers of breast cancer patients

BackgroundExposure to polychlorinated biphenyls (PCBs) has been shown to influence expression of some biomarkers that are predictive/prognostic for breast cancer. Therefore, our study was conducted to further investigating associations of different functional PCBs in adipose tissue with breast cancer prognostic biomarkers. MethodsTwo hundred and five breast cancer patients were recruited in Shantou, China. Breast adipose tissues were collected during their resection surgery and levels of 7 PCB congeners were analyzed by gas chromatography-mass spectrometry (GC-MS). The PCB congeners were divided into 4 groups according to structure-activity. Socio-demographic, clinical and pathological information were obtained from questionnaire and digital medical records. Odds ratios (ORs) for associations between prognostic biomarkers and PCB levels (tertile 3 [T3], tertile 2 [T2] vs. tertile 1) were estimated from logistic regression models. ResultsMost PCB congeners were detectable, with a highest level (22.06 ng/g lipid) of PCB153. As for estrogenic PCBs, increased PCB52 exposure was positively associated with PR expression (ORT2 = 2.36, Ptrend = 0.054), but higher PCB101 level was negatively associated with HER-2 (ORT3 = 0.24, Ptrend = 0.029) and tumor size (OR = 0.43). Limited dioxin-like PCB138 exposure was positively associated with ER (ORT2 = 3.23, ORT3 = 3.77, Ptrend = 0.047) but negatively with Top-IIα expression (ORT2 = 0.35, ORT3 = 0.28, Ptrend = 0.080). Higher PCB153 (CYP inducer) level was negatively associated with ER (ORT2 = 0.32, ORT3 = 0.19, Ptrend = 0.038) but positively with Ki-67 expression (ORT2 = 1.43, ORT3 = 3.60, Ptrend = 0.055). Higher neurotoxic PCB28 was positively associated with HER-2 (ORT3 = 5.43, Ptrend = 0.006) and tumor size (OR = 2.37). Moreover, total PCBs exposure was positively associated with VEGF-C (ORT2 = 76.91, ORT3 = 97.96, Ptrend = 0.041) and tumor metastasis (OR = 2.25). ConclusionsDifferent functional PCB congeners have different associations (both positive and negative) with breast cancer prognostic biomarkers, as well as tumor classification stage. Therefore, the development and aggressiveness of breast cancer may depend upon exposure to specific structure-activity of PCBs.

Non-dioxin-like Polychlorinated Biphenyls (PCBs) and Chlordecone Release from Adipose Tissue to Blood in Response to Body Fat Mobilization in Ewe (Ovis aries)

Understanding how persistent organic pollutants (POPs) are released from adipose tissue (AT) to blood is a critical step in proposing rearing strategies hastening the removal of POPs from contaminated livestock. The current study aimed to determine in nonlactating ewes whether polychlorinated biphenyls (PCBs) and chlordecone are released from AT to blood along with lipids during body fat mobilization achieved through β-agonist challenges or undernutrition. β-Agonist challenges did not affect serum POP concentrations, whereas serum PCBs 138, 153, and 180 were readily increased in response to undernutrition. After 21 days of depuration in undernutrition, AT PCB 153 and 180 concentrations were increased concomitantly with a decrease in adipocyte volume, whereas AT chlordecone concentration was not different from that observed at the end of the well-fed contamination period. Thus, undernutrition may be of practical relevance for accelerating POP depuration unless it is combined with a strategy increasing their excretion pool.

In Utero Exposure to Environmentally Relevant Concentrations of PCB 153 and PCB 118 Disrupts Fetal Testis Development in Sheep

Polychlorinated biphenyls (PCB) are environmental pollutants linked to adverse health effects including endocrine disruption and disturbance of reproductive development. This study aimed to determine whether exposure of pregnant sheep to three different mixtures of PCB 153 and PCB 118 affected fetal testis development. Ewes were treated by oral gavage from mating until euthanasia (d 134), producing three groups of fetuses with distinct adipose tissue PCB levels: high PCB 153/low PCB 118 (n = 13), high PCB 118/low PCB 153 (n = 14), and low PCB 153/low PCB 118 (n = 14). Fetal testes and blood samples were collected for investigation of testosterone, testis morphology, and testis proteome. The body weight of the offspring was lower in the high PCB compared to the low PCB group, but there were no significant differences in testis weight between groups when corrected for body weight. PCB exposure did not markedly affect circulating testosterone. There were no significant differences between groups in number of seminiferous tubules, Sertoli cell only tubules, and ratio between relative areas of seminiferous tubules and interstitium. Two-dimensional (2D) gel-based proteomics was used to screen for proteomic alterations in the high exposed groups relative to low PCB 153/low PCB 118 group. Twenty-six significantly altered spots were identified by liquid chromatography (LC)–mass spectroscopy (MS)/MS. Changes in protein regulation affected cellular processes as stress response, protein synthesis, and cytoskeleton regulation. The study demonstrates that in utero exposure to different environmental relevant PCB mixtures exerted subtle effects on developing fetal testis proteome but did not significantly disturb testis morphology and testosterone production.

Fetal adrenal development: Comparing effects of combined exposures to PCB 118 and PCB 153 in a sheep model

This study investigated the effects of exposure to the ubiquitous contaminants polychlorinated biphenyls (PCBs) on the fetal adrenal cortex and on plasma cortisol using the domestic sheep (Ovis aries) as a model. Pregnant ewes were intendedly subjected to oral treatment with PCB 153 (98 μg/kg bw/day), PCB 118 (49 μg/kg bw/day) or the vehicle corn oil from mating until euthanasia on gestation day 134 (±0.25 SE). However, because of accidental cross-contamination occurring twice causing a mixed exposure scenario in all three groups, the focus of this paper is to compare three distinct groups of fetuses with different adipose tissue PCB levels (PCB 153high, PCB 118high and low, combined groups) rather than comparing animals exposed to single PCB congeners to those of a control group. When comparing endocrine and anatomical parameters from fetuses in the PCB 153high (n = 13) or PCB 118high (n = 14) groups with the low, combined group (n = 14), there was a significant decrease in fetal body weight (P < 0.05), plasma cortisol concentration (P < 0.001) and adrenal cortex thickness (P < 0.001). Furthermore, adrenal weight was decreased and plasma ACTH was increased only in the PCB 118high group. Expression of several genes encoding enzymes and receptors related to steroid hormone synthesis was also affected and mostly down-regulated in fetuses with high PCB tissue levels. In conclusion, we suggest that mono-and di-ortho PCBs were able to interfere with growth, adrenal development and cortisol production in the fetal sheep model. © 2011 Wiley Periodicals, Inc. Environ Toxicol, 2013.

Predictors of Polychlorinated Biphenyl Concentrations in Adipose Tissue in a General Danish Population

Polychlorinated biphenyls (PCBs) are ubiquitously present in the environment and suspected of carcinogenic, neurological, and immunological effects. Our purpose was to identify predictors of adipose tissue levels of mono-, di-, and tri-ortho-substituted PCBs experienced by a general population and to establish whether predictors vary according to substitution group. In this study of 245 randomly selected persons from a prospective Danish cohort of 57,053 persons, we examined geographical area, age, lactation, BMI, and intake of eight major dietary groups as potential determinants of adipose concentrations of mono-, di-, and tri-ortho-substituted PCBs by linear regression analyses. Lactation, BMI, and intake of fruit, vegetables, and dairy products showed negative associations with PCB concentrations in adipose tissue in all models, and living in Copenhagen city, age, and consumption of fish (particularly fatty fish) were positively associated. The associations between several of the predictors and mono-ortho-substituted PCBs tended to differ from the associations found for di- and tri-ortho-substituted PCBs. In conclusion, geography, age, lactation, BMI, and consumption of fatty fish consistently predicted the concentration of PCBs in adipose tissue. Our results indicate that predictors of PCBs varied according to substitution group, suggesting that ortho-substituted groups should be analyzed separately.

Multivariate models to predict human adipose tissue PCB concentrations in Southern Spain

The use of Polychlorinated biphenyls (PCBs) has been severely restricted due to their high toxicity and persistency in the environment. However, the presence of PCBs in human tissues nowadays is still been reported worldwide. Background exposure predictors of the human PCB body burden require more precise understanding. In the present study, PCB congeners 138, 153, and 180 were quantified in adult adipose tissue samples ( n = 387) from Granada Province (Southern Spain) and data on potential predictors of PCB concentrations were gathered by questionnaire. Chemical analysis of the selected congeners was done by gas chromatography and mass spectrometry, and multivariate analyses were performed stratifying by gender. PCB residues were quantified in 92% (PCB 153), 90% (PCB 180), and 86% (PCB 138) of the population. Geometric mean concentrations were 161.65 ± 4.41 ng/g lipid for PCB 153, 111.62 ± 6.27 ng/g lipid for PCB 180, and 38.41 ± 8.61 ng/g lipid for PCB 138. Multivariate models explained 30–36% of the variability in PCB concentrations. Age and body mass index (BMI) predicted exposure in both males and females and were positively correlated with the concentration of the three PCB congeners. Occupation and diet predicted exposure in the males, whereas only dietary predictors were observed in the females. Further in-depth studies are required to investigate the influence of dietary habits on the bioaccumulation of PCBs and to evaluate the impact of policies aimed at reducing human exposure.

Determination of organochlorine pesticide and polychlorinated biphenyl levels in adipose tissue of infertile men

During the recent two decades, a remarkable drop in fertility rates has been noticed almost all over the world. A series of studies have showed that environmental factors had the primary role causing the observed adverse trends in the male reproductive health problems. Especially chlorinated hydrocarbons, for instance polychlorinated biphenyls (PCB) and pesticides, could mimic or antagonize the effects of steroid hormones, like estrogens and androgens and possibly interfering with male reproductive capacity. Organochlorine pesticides (OCPs) (i.e. p.p'-DDT, endosulfan...) and PCBs are widespread used chemicals in agriculture and industry for different purposes all over the world. Although direct evidence is lacking, theoretical considerations and epidemiological evidence implicate these compounds as potential hazards to human and wildlife reproductive health. For this purpose, in this study adipose tissue samples have provided from healthy males which were diagnosed as infertile men living in Ankara, Turkey at least for 5 years. Residual levels of OCPs (alpha-BHC, beta-BHC, gamma-BHC, HCB, Endosulfan I, II, p,p'-DDE, and p,p'-DDT) and seven major persistent PCB congeners (PCB 28, 52, 101, 118, 138, 153, and 180) were measured in 25 infertile men and 21 healthy men's adipose tissue samples by GC-ECD. Levels of OCPs and PCBs in adipose tissue of infertile men compared with those provided from controls. When the concentrations of each of the OCP were compared between the fertile and infertile groups, no statistical significance was obtained. Concentrations of each of the PCB congeners were compared between the fertile and infertile groups, no statistical significance was obtained (p > 0.05), except for 2,2',5,5'-Tetrachlorobiphenyl (PCB 52) (p = 0.032) and 2,2',3,4,4',5,5'-heptachlorobiphenyl (PCB 180) (p = 0.017).

Multivariate Data Analyses of Persistent Organic Pollutants in Maternal Adipose Tissue in Singapore

Persistent organic pollutants (POPs) were detected in 88 maternal adipose tissue samples collected during year 2004 to 2006, in Singapore. Organochlorine pesticides (OCPs) were the most dominant followed by polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). Multivariate data analyses (MVA) including principal component analysis (PCA), partial least-squares regression (PLSR), and partial least-squares discriminant analysis (PLS-DA) were applied to elucidate the relationship between concentrations of POPs in adipose tissues and donors' characteristics. Food consumption played the most significant role in accounting for levels of POPs in adipose tissue. Fish and poultry consumption was the route of PCBs and PBDEs in mothers in Singapore, while beta-HCH came mainly from vegetables. An age-dependent accumulation of POPs was found for beta-HCH and PCB congeners, and lactation and gestation functioned as a decontamination processes for PCBs in adipose tissue. Gestational diabetes mellitus (GDM) may change the profile of POPs in adipose tissue, probably due to an alteration in lipid metabolism. POPs investigated here may not be the cause of antenatal complication in pregnant women, and baby gender was not related to the pattern of contaminants in maternal adipose tissue.

Concentrations of Polychlorinated Dibenzo-p-Dioxins (PCDDs), Polychlorinated Dibenzofurans (PCDFs), and Dioxin-Like PCBs in Adipose Tissue of Infertile Men

Some epidemiological studies suggested the occurrence of an alteration in the male reproductive function in the past 50 years, particularly a decrease in the sperm count and quality, an increase in the malformations frequency of the reproductive apparatus (cryptorchidism and hypospadias) and of testicular cancers. Especially according the laboratory animals studies, polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) have been suspected to play a crucial and deleterious role in the alteration of human fertility. For this reason, we measured adipose tissue concentrations of PCDDs/Fs and dioxin-like PCBs in 23 fertile and 22 infertile men living in Ankara, Turkey. Adipose tissue samples were analyzed for PCDD/F and 12 dioxin-like PCB congeners using high-resolution gas chromatography/high-resolution mass spectrometry. For the fertile and infertile groups, the World Health Organization (WHO)(PCDD/F)-TEQ concentrations ranged from 3.0 to 15.8 pg/g fat and from 2.8 to 17.2 pg/g fat, respectively (4.4-31.5 and 4.7-22.3 WHO-TEQs/g fat, respectively, including dioxin-like PCBs) (p > 0.05). The mean concentrations of WHO(PCDD/F)-TEQ and WHO(PCB)-TEQ have been calculated as 7.2 and 12.5 pg/g (on a lipid basis) for the fertile group and 7.0 and 9.4 pg/g for the infertile group, respectively. Concentrations of each of the PCDD/F and dioxin-like PCB congeners were compared in fertile and infertile groups among themselves, and no statistical significance was obtained (p > 0.05), except 2,3,7,8-tetrachlorodibenzofuran (p = 0.0029) and 1,2,3,4,6,7,8,9-octachlorodibenzofuran (p = 0.01).

Polychlorinated biphenyls (PCBs) and hydroxy-PCBs in adipose tissue of women in Southeast Spain

Polychlorinated biphenyls (PCBs) and hydroxylated PCBs (OH-PCBs) were investigated in human adipose tissue samples collected from 20 women undergoing surgery. Mean sum of PCB and sum of OH-PCB levels were 737 ng/g of lipid and 8 pg/g of lipid, respectively. Among PCBs, congeners 180, 153, 138 and 170 were the most frequent and abundant, and together constituted 72% of the total amount of PCBs in adipose tissue. The PCB congener pattern and the frequencies and concentrations of non-dioxin-like and non-hydroxylated congeners observed in adipose tissue were similar in distribution and order of magnitude to the profile previously published in Spain but lower than that found in other European countries. Among OH-PCB congeners studied, 4-OH-PCB 107/118 was found at the highest concentrations followed by 3′-OH-PCB 180 and 3-OH-PCB 138. To date, no information on levels of PCB metabolites in the Spanish population is available for comparison. These three predominant OH-PCBs contributed 97% of all OH-PCBs. Twelve dioxin-like PCBs contributed around 8% of the total PCB exposure, and all were present in all study subjects. Further research is required to determine trends in human exposure to PCBs and OH-PCBs and how existing banning measures affect exposure.

Physiologically Based Modeling of the Accumulation in Plasma and Tissue Lipids of a Mixture of PCB Congeners in Female Sprague-Dawley Rats

This study aimed to develop a physiologically based model for simulating the concentrations of polychlorinated biphenyls (PCBs) in tissue and plasma lipids of rats exposed to PCB mixtures. The model was based on the assumption that the neutral lipid fraction is the only critical determinant of the tissue distribution of PCBs, and that the solubility/retention in other tissue components is negligible. The volumes of the model compartments reflected the volumes of neutral lipids, whereas the flow rates corresponded to those of the neutral lipids in blood. Since the equilibrium ratio of PCB concentrations in neutral lipids of tissues and plasma equals 1, the present modeling approach does not require the use of tissue:blood partition coefficients. Metabolism rates were derived from the best visual fit of the model to the PCB concentrations in hepatic lipids determined on d 41 and 90 in rats exposed to a mixture containing 5, 50, or 500 μg PCBs (118, 138, 153, 170, 180 and 187) per kilogram body weight according to various protocols: (a) every-day dosing, (b) once-a-week dosing, (c) consecutive dosing for 13 d with no further treatment, and (d) 13 irregularly spaced doses. The resulting model consistently simulated the concentrations of PCBs in adipose tissue and plasma lipids of rats exposed according to the four described protocols. The physiologically based pharmacokinetic (PBPK) model developed in this study should be useful as a basis for interpretating blood or plasma lipid concentration data on PCBs collected during biomonitoring studies.

Dietary predictors of concentrations of polychlorinated biphenyls in breast adipose tissue of women living in Ontario, Canada.

The authors evaluated dietary predictors of concentrations of 11 polychlorinated biphenyls (PCBs) in breast adipose tissue from 190 women with benign breast disease who live in Ontario, Canada. Consumption of fish was positively correlated with, and the most consistent dietary predictor of, breast tissue PCB levels. Dietary predictors accounted for < 8% of the variation in breast adipose tissue PCB levels. Age was positively and most strongly associated with tissue PCB levels, perhaps representing long-term dietary intake and the complex interplay of absorption, metabolism, distribution, and excretion.

Congener-specific data of polychlorinated biphenyl residues in human adipose tissue in Poland

Adipose tissue of inhabitants of the Gdańsk city located at the southern coast of the Baltic Sea and the province of Skierniewice of inland Poland have been investigated for congeners of polychlorinated biphenyls (PCBs) by the capillary GC-MS technique. PCB IUPAC No. 153 was a high contributor of the congener occupying 23% of the total PCB content, and together with No. 138 of 18% and No. 180 of 13% were the most prevalent members. Samples taken from Gdańsk citizens in 1990 contained 1.5 ± 1.3 μg/g of total PCBs on a fat weight basis while the citizens from the province of Skierniewice, sampled in 1979, contained 1.2 ± 0.4 μg/g, which seemed to indicate a persistent PCB exposure in Poland. Among Gdańsk citizens, randomly selected autopsy samples of liver cancer from dead persons contained 4.7 μg/g of PCBs, while in all other samples the level was between 0.75 and 1.9 μg/g of PCBs. TCDD TEQ of 13 detectable coplanar members of PCBs in adipose tissue of Gdańsk, and Skierniewice inhabitants, was 210 and 190 pg/g on a lipid weight basis, respectively, including 45 and 59 pg/g of non- ortho, 142 and 110 pgg/g of mono- ortho and 24 and 16 pg/g of di- ortho chlorobiphenyls. A fingerprint of chlorobiphenyl composition in the samples examined was virtually the same for human adipose tissue taken in 1990 from the coastal city of Gdańsk and in 1979 from the inland province of Skierniewice, in spite of geographic variations and sampling intervals.

Documenting Temporal Trends of Polychlorinated Biphenyls in the Environment

In the 15 years since the regulation of polychlorinated biphenyls (PCBs) in the United States, numerous studies have been undertaken to assess PCB levels in the environment. This report reviews the available data from published literature and government agency reports on temporal trends of PCB levels in various environmental compartments. Adequate data were identified to discuss PCB trends in foods for human consumption, human adipose tissue, human blood sera, various fish species, and shellfish. The review found that PCB levels in the human diet currently are less than 1% of the levels detected in the early 1970s as measured by the nationwide Total Diet Study of the FDA. Similarly, EPA data indicate a decrease in the percentage of persons with over 1 ppm of PCBs in adipose tissue from 62% in 1972 to 2% in 1984 when the study was terminated. Studies by the National Oceanic and Atmospheric Administration (NOAA) and other groups hase shown a 2- to 10-fold decline in PCB contamination in fish and shellfish from the early 1970s to the late 1980s. The most dramatic declines across all environmental compartments appear in the late 1970s to the mid-1980s which corresponds to the time frame when regulatory controls were imposed by the Toxic Substances Control Act (TSCA). These declines are expected to continue but at slower rates.

Assessment of exposure to polychlorinated biphenyls: Analysis of selected isomers in blood and adipose tissue

Concentrations of 12 selected polychlorinated biphenyl (PCB) congeners and isomers in human serum and adipose tissue after environmental and short- and long-term occupational exposures were determined. The individual congener concentrations in adipose tissue varied between less than 0.01 and 420 micrograms/kg (tri-, tetra-, penta-, hexa-, and heptachlorobiphenyls); the dominating isomers were 2,2',4,4',5,5'- and 2,2',3,4,4',5'-hexaCB, which represented approximately 90% of all PCBs in adipose tissue. Those isomers were also the most abundant in serum specimens after environmental exposure, their contribution together with the 2,2',3,4,4',5',6-heptaCB was approximately 90%. After short-term as well as long-term occupational exposure, the most remarkable changes were observed in the concentrations of the tri- and tetrachlorobiphenyls. In long-term occupational exposure 2,4,4'-triCB (mean 3.15 micrograms/liter) and 2,4,4',5-tetraCB (mean, 9.4 micrograms/liter) showed the highest concentrations, whereas after short-term exposure 2,2',5-tri- (mean 2.04 micrograms/liter) and 2,3',4,4'-tetraCB (mean 1.5 micrograms/liter) were most abundant. In people with only environmental exposure, the concentrations in adipose tissue of some PCB isomers were interrelated. The concentrations of the isomers 2,4,4'5-tetraCB (IUPAC 74), 2,2',4,4',5,5'-hexaCB (IUPAC 153), 2,2',3,4,4'5'-hexaCB (IUPAC 138), 2,3,3',4,4',5-hexaCB (IUPAC 156), 2,2',3,4,4',5',6-heptaCB (IUPAC 183), and 2,2',3,3',4,4',5-heptaCB (IUPAC 171) showed close correlation, the coefficients varied from 0.42 to 0.98. The correlation between the concentrations of individual PCB isomers in adipose tissue was highest for 2,4-substituted highly chlorinated isomers, i.e., isomers with longest half-times in the body.

Accumulation of a commercial polychlorinated biphenyl mixture (aroclor 1016) in adult rhesus monkeys and their nursing infants

Female rhesus monkeys (24) were divided into 3 groups and fed diets calculated to contain 1.0, 0.25 or 0 parts per million (ppm) of a commercial mixture of polychlorinated biphenyls (PCBs), Aroclor 1016. The animals consumed a calculated total of 18.1±3.1, 4.5±0.6 and 0 mg Aroclor 1016/kg of body weight over the 87±9 week experimental period. All animals were bred, conceived and experienced uncomplicated pregnancies. The birth weights of the infants born to females receiving the 1.0 ppm PCB diets were significantly less than those of the control infants. There was a positive relationship between the levels of Aroclor 1016 in the tissues and the dose administered in the diets. Aroclor 1016 content of infant tissues was consistent with maternal adipose tissue PCB levels. The content of Aroclor 1016 in the milk fat of the animals more closely approximated that in the individual's adipose tissue than in the serum. At weaning, the mesenteric fat of the experimental infants contained concentrations of Aroclor 1016 which were 4–7 times that found in the mothers. Analyses of the tissues and fluids of the experimental animals demonstrated accumulation of PCB isomerides. The number of isomerides present and the ratio of those detected differed between adult and infants as well as between milk and serum. After weaning, the pattern ofAroclor 1016 isomerides present in the infant's adipose was similar to that observed at weaning although the concentrations had decreased.

Induction of mouse and rat liver microsomal enzymes by polychlorinated biphenyls and its relations to the PCB levels in the tissue

Kanechlor (KC)-300, 400, 500, and 600 consisting of polychlorinated biphenyls (PCB) containing 43, 48, 55, and 61% chlorine respectively, were administered in a single dose of 100 mg/kg to mice and rats. The effect of PCB was investigated by determining pentobarbital sleeping time, liver microsomal hemoprotein contents, PCB level and gaschromatography (GC) pattern in tissue. Pentobarbital sleeping time was prolonged 2 to 4 times longer than that of control level after 3 to 4 hr of KC treatment in both ICR and ddN strain mice and KC-300 was the most effective. Forty-eight hr after treatment, however, this sleeping time was half that of the control. Sleeping time in ICR strain mice returned to control level 8 days after the treatment with KC-300 and KC-500, but the decrease in sleeping time continued in ddN mice. Conversely, the prolongation of sleeping time in rats was only 20% the control level at 3 hr after KC-300 treatment, but the shortening of sleeping time was more marked than in mice. Both the prolongation of sleeping time in mice treated with KC-300 and the shortening of sleeping time in rats treated wiht KC-500 were more rapidly effected when an oral dose rather than when a intraperitoneal one was given. Induction of liver microsomal cytochrome P-450 level was maximum in rats treated with KC-600 and increase of hemoprotein level and shortening of sleeping time were proportional to the chlorine content of PCB. The CO-difference spectrum of microsomes from rats treated with KC had an absorbance maximum at 448 nm. Direct relationship between storage of PCB in adipose tissue and the induced effect by KC has also been demonstrated in rats. PCB level in the liver of rats was higher for about 8 hr after KC-500 treatment given orally and was lower than the PCB level in adipose tissue after 8 hr. The GC-pattern of PCB stored in tissues was different from that of standard KC, indicating that all components were not metabolized at the same rate and that the components of the KC with the longer retention time were metabolized to a lesser degree than those with the shorter retention time.