Levels and spatial profile of per- and polyfluoroalkyl substances in edible shrimp products from Japan and neighboring countries; a potential source of dietary exposure to humans.

Exposure to per- and polyfluoroalkyl substances (PFAS) is of great concern for human health because of their persistence and potentially adverse effects. Dietary intake, particularly through aquatic products, is a significant route of human exposure to PFAS. We analyzed perfluoroalkyl sulfonic acid (PFSA with carbon numbers from 6 to 8 and 10 (C６-C8, C10)) and perfluorooctanesulfonamide (FOSA), and perfluoroalkyl carboxylic acid (PFCA with carbon numbers from 6 to 15 (C6-C15)) in 30 retail packs of edible shrimps, which included seven species from eight coastal areas of Japan and neighboring countries. The most prevalent compounds were perfluorooctane sulfonate (PFOS, C8) and perfluoroundecanoic acid (PFUnDA, C11), accounting for 46 % of total PFAS. The concentrations ranged from 6.5 to 44 ng/g dry weight (dw) (equivalent to 1.5 to 10 ng/g wet weight (ww)) and varied according to species and location. For example, Alaskan pink shrimp (Pandalus eous) from the Hokuriku coast, Japan contained high levels of long-chain PFCAs (38 ng/g dw (equivalent to 8.7 ng/g ww)), while red rice prawn (Metapenaeopsis barbata) from Yamaguchi, Japan contained a high concentration of PFOS (29 ng/g dw (equivalent to 6.7 ng/g ww)). We also observed regional differences in the PFAS levels with higher concentrations of long-chain PFCAs in Japanese coastal waters than in the South China Sea. The PFAS profiles in shrimp were consistent with those in the diet and serum of Japanese consumers, suggesting that consumption of seafood such as shrimp may be an important source of exposure. The estimated daily intake of sum of all PFAS from shrimp from Japanese coastal water was 0.43 ng/kg body weight/day in average, which could reach the weekly tolerable values (4.4 ng/kg body weight /week) for the sum of the four PFSA set by the EFSA for heavy consumers. The high concentration of PFAS in shrimp warrants further investigation.

Profiles and determinants of dicofol, endosulfans, mirex, and toxaphenes in breast milk samples from 10 prefectures in Japan.

Human exposure to persistent organic pollutants (POPs) is reflected by POP concentrations in breast milk. Many studies of POPs in breast milk have been performed in Japan, but insufficient information is available about some legacy POPs (e.g., mirex and toxaphenes, included in the Stockholm Convention in 2001) and novel POPs (e.g., dicofol and endosulfans, included in the Stockholm Convention in 2019 and 2011, respectively). In this study, dicofol, endosulfan, mirex, and toxaphene concentrations in breast milk from 10 prefectures in Japan were determined. The samples were collected between 2005 and 2010, before Stockholm Convention restrictions on endosulfans and mirex were implemented. Common POPs (e.g., polychlorinated biphenyls) were also analyzed to allow the contamination statuses to be compared. The α-endosulfan and ß-endosulfan concentrations were 0.26-13 and 0.012-0.82 ng/g lipid, respectively. The toxaphene #26 and #50 concentrations were <0.08-5.6 and < 0.1-8.5 ng/g lipid, respectively. The dicofol concentrations were <0.01-4.8 ng/g lipid. The mirex concentrations were <0.2-3.5 ng/g lipid. The α- and ß-endosulfan concentrations on a lipid weight basis negatively correlated with the lipid contents of the milk samples (ρ = -0.65, p < 0.01 for α-endosulfan; ρ = -0.58, p < 0.01 for ß-endosulfan). The toxaphene concentrations positively correlated with the lipid contents. The mirex concentrations positively correlated with the maternal age but negatively correlated with the maternal body mass index. No correlations between the dicofol concentrations and the factors were found. Principal component analysis divided the data into four groups, (1) chlordanes, dichlorodiphenyltrichloroethanes and related compounds, hexachlorobenzene, hexachlorocyclohexanes, hexachloroethane, and polychlorinated biphenyls, (2) endosulfans, (3) dicofol, dieldrin, and toxaphenes, and (4) bromodiphenyl ether 47. This indicated that bromodiphenyl ether 47, dicofol, endosulfans, and toxaphenes have different exposure routes or different kinetics to the other legacy POPs.

Effects of perfluoroalkyl carboxylic acids on the uptake of sulfobromophthalein via organic anion transporting polypeptides in human intestinal Caco-2 cells.

We performed a detailed investigation of the uptake of sulfobromophthalein (BSP) from the apical membrane of Caco-2 cells, which is a substrate for organic anion transporting polypeptides (OATPs), and calculated the kinetic parameters of BSP uptake as follows: Km = 13.9 ± 1.3 µM, Vmax = 1.15 ± 0.07 nmol (mg protein)-1 (5 min)-1, and kd = 38.2 ± 0.53 µL (mg protein)-1 (5 min)-1. Coincubation with medium-chain (C7-C11) perfluoroalkyl carboxylic acids (PFCAs), such as perfluoroheptanoic acid (PFHpA, C7), perfluorooctanoic acid (PFOA, C8), perfluorononanoic acid (PFNA, C9), perfluorodecanoic acid (PFDA, C10) and perfluoroundecanoic acid (PFUnDA, C11), significantly decreased BSP uptake by 27-55%, while coincubation with short- (C3-C6) and long-chain (C12-C14) PFCAs decreased the uptake only slightly. Dixon plotting suggested that PFOA, PFNA and PFDA competitively inhibited the BSP uptake with inhibition constant (Ki) values of 62.2 ± 1.3 µM, 35.3 ± 0.1 µM and 43.2 ± 0.3 µM, respectively. PFCAs with medium-chains could be substrates for OATPs, probably OATP2B1, which is the most abundantly expressed OATP isoform in Caco-2 cells.

Kanechlor 500-mediated changes in serum and hepatic thyroxine levels primarily occur in a transthyretin-unrelated manner.

The effects of Kanechlor-500 (KC500) on the levels of serum total thyroxine (T4 ) and hepatic T4 in wild-type C57BL/6 (WT) and its transthyretin (TTR)-deficient (TTR-null) mice were comparatively examined. Four days after a single intraperitoneal injection with KC500 (100 mg/kg body weight), serum total T4 levels were significantly decreased in both WT and TTR-null mice. The KC500 pretreatment also promoted serum [125 I]T4 clearance in both strains of mice administrated with [125 I]T4 , and the promotion of serum [125 I]T4 clearance in WT mice occurred without inhibition of the [125 I]T4 -TTR complex formation. Furthermore, the KC500 pretreatment led to significant increases in liver weight, steady-state distribution volume of [125 I]T4 , hepatic accumulation level of [125 I]T4 , and concentration ratio of the liver to serum in both strains of mice. The present findings indicate that the KC500-mediated decrease in serum T4 level occurs in a TTR-unrelated manner and further suggest that KC500-promoted T4 accumulation in the liver occurs through the development of liver hypertrophy and the promotion of T4 transportation from serum to liver.

Possible mechanism for the polychlorinated bipheny-linduced liver-selective accumulation of thyroxine in rats.

We have previously reported that decrease in level of serum thyroxine T4 by Kanechor 500 (KC500) in rats would occur through the increase in hepatic T4 accumulation rather than the increase in hepatic T4-glucuronyl transferase activity. In the present study, to understand the mechanism underlying the KC500-mediated increase in hepatic T4 accumulation, we examined the relationship between the KC500-mediated changes in hepatic T4 accumulation and the expression levels of mRNAs of hepatic transporters including T4 transporters. [125I]T4 was intravenously injected into KC500-pretreated and control (KC500-untreated) Wistar rats, and [125I]T4 uptake levels of liver parenchymal cells were comparatively examined. The amount of [125I]T4 uptake by hepatic cells increased in a time-dependent manner up to 96 hr after KC500 treatment. Following KC500 treatment, a time-dependent increase in the mRNA level of hepatic T4 influx transporter LAT1 was observed up to 96 hr later, while a significant increase in hepatic T4 influx transporter Oatp2 mRNA occurred only at 96 hr later. No KC500-mediated increases in the mRNAs of other hepatic transporters (Oatp1, Oatp3, Oatp4, Ntcp, LAT2, and Mrp2) were observed at any timepoints, although the mRNA expression of the T4 conjugate(s) efflux transporter Mrp3 significantly increased in a time-dependent manner 24-96 hr following KC500 treatment. The present findings suggest that KC500-mediated increase in hepatic T4 accumulation occurs, at least in part, through the increase in the expression of hepatic T4-transporters, such as LAT1 and Oatp2.

Growth-related changes in non-essential and essential metals in the liver of star-spotted smooth-hounds (dogfish) Mustelus manazo from the northern region of Japan.

We analyzed Cd, Hg, Zn, Cu, Mn and Fe concentrations in liver samples from male and female star-spotted smooth-hounds at various life stages. Male sharks of this species are known to reach their maximum body length (BL) more quickly than females, while females are known to mature later and live longer than males. Hepatic Cd and Hg concentrations in males and females markedly increased after maturation, but these increases proceeded earlier in males than in females. Hepatic Zn and Cu concentrations decreased during the growth stage of males and females, and thereafter increased concomitantly with increases of Cd and Hg burdens, forming a U-shaped curve over their lifespan, and the BL at which the lowest concentrations of Zn and Cu were observed was smaller in males than in females. These gender-related differences in those metals could reflect the faster growth and earlier cessation of growth in males.

Uptake of perfluorooctanoic acid by Caco-2 cells: Involvement of organic anion transporting polypeptides.

The mechanism underlying the intestinal absorption of perfluorooctanoic acid (PFOA) was investigated using Caco-2 cells. The uptake of PFOA from the apical membrane of Caco-2 cells was fast, and pH, temperature, and concentration dependent, but Na+ independent. Coincubation with sulfobromophthalein (BSP), glibenclamide, estron-3-sulfate, cyclosporine A or rifamycin SV, which are typical substrates or inhibitors of organic anion transporting polypeptides (OATPs), significantly decreased the uptake of PFOA. However, coincubation with probenecid or p-aminohippuric acid, typical substrates of organic anion transporters, did not decrease the uptake of PFOA. Furthermore, coincubation with l-lactic acid or benzoic acid, substrates of monocarboxylic acid transporters, did not decrease PFOA uptake. The relationship between the initial uptake of PFOA and its concentration was saturable, suggesting the involvement of a carrier-mediated process. The calculated Km and uptake clearance (Vmax/Km) values for PFOA were 8.3µM and 55.0µL/mg protein/min, respectively. This clearance value was about 3-fold greater than that of the non-saturable uptake clearance (Kd: 18.1µL/mg protein/min). Lineweaver-Burk plots revealed that BSP competitively inhibits the uptake of PFOA, with a Ki value of 23.1µM. These results suggest that the uptake of PFOA from the apical membranes of Caco-2 cells could be, at least in part, mediated by OATPs along with BSP.

[Massive Air Inflow into the Left Ventricle Detected by Transesophageal Echocardiography during Rastelli Coduit Re-replacement].

We present a case of massive air inflow into the left ventricle from the right ventricle through a small intraventricular shunt detected by transesophageal echocardiography (TEE). This case suggests that TEE plays an important role in the right ventricle-pulmo- nary artery conduit re-replacement.

Effect of quercetin on the uptake and efflux of aristolochic acid I from Caco-2 cell monolayers.

OBJECTIVE: The purpose of this study was to determine whether quercetin decreases the uptake of aristolochic acid I (AAI) from the apical membranes of Caco-2 cells via H(+) -linked MCTs at neutral pH as well as to confirm the secretion of AAI through the Caco-2 cell monolayers via ABC transporters. METHODS: Caco-2 cells cultured on the dishes or permeable membranes were incubated with AAI in the absence or presence of quercetin or transporter inhibitors. KEY FINDINGS: Coincubation with quercetin decreased the uptake of AAI by Caco-2 cells cultured on the dishes at pH 7.4, and a similar decrease in AAI uptake was found when the cells were coincubated with acetic acid or benzoic acid. In contrast, the basolateral-to-apical transport of AAI was higher than the apical-to-basolateral transport of AAI at pH 7.4, and the former transport was decreased by quercetin and the BCRP inhibitors of Ko-143 and mitoxantrone, but not by P-gp or MRP2 inhibitors. CONCLUSIONS: AAI appears to be secreted from the apical membranes of Caco-2 cells via BCRP at neutral pH, although a small amount of AAI is taken up from the apical membranes via H(+) -linked MCTs, and quercetin may decrease both the BCRP-mediated efflux and the MCT-mediated influx of AAI.

Metal Concentrations in the Liver and Stable Isotope Ratios of Carbon and Nitrogen in the Muscle of Silvertip Shark (Carcharhinus albimarginatus) Culled off Ishigaki Island, Japan: Changes with Growth.

We analyzed Hg, Cd, Zn, Cu and Fe concentrations in liver samples as well as the Hg concentration and stable isotope ratios of carbon and nitrogen (δ13C and δ15N) in muscle samples from silvertip sharks (Carcharhinus albimarginatus) in Japan. Muscular and hepatic Hg concentrations increased with increased body length. However, these increases were more prominent in the liver than in the muscle samples, and appeared to occur after maturation. Hepatic Zn and Cu concentrations decreased during the growth stage, and then increased concomitantly thereafter with increases in Cd burden. Hepatic Fe concentration from males increased proportionally with increases in body length, whereas no increase was observed in samples from females, probably due to the mother-to-embryo transfer of Fe. The δ13C values tended to decrease with increases in body length, whereas no decrease in the δ15N values was observed.

[Metabolism of 2,2',3,4,4',5,5'-Heptachlorobiphenyl (CB180) by Animal Liver Microsomes].

The in vitro metabolism of 2,2',3,4,4', 5,5'-heptachlorobiphenyl (CB180) was examined using liver microsomes of rats, guinea pigs and hamsters. Of liver microsomes from untreated animals, rats and guinea pigs produced one metabolite (M-1) with the activity of 1.2 and 18.1 pmol/hr/mg protein, respectively, but hamsters did not at all. Pretreatment of phenobarbital (PB) resulted in about 32-fold increase in rats, 4-fold increase in guinea pigs and an appearance of M-1 in hamsters (15 pmol/hr/mg protein). In addition, another metabolite (M-2) was formed only by liver microsomes of PB-treated guinea pigs. In contrast, pretreatment of 3-methylcholanthrene showed no metabolite in three animals. By comparison of the GC-MS data of the metabolites with synthesized authentic samples, M-1 and M-2 was determined to be 3'-hydroxy (OH)-CB180 and 4'-OH-2,2',3,4,5,5'-hexachlorobiphenyl (CB141), respectively. These results suggest that 3'-OH-CB180 is a major metabolite and is formed by PB-inducible cytochrome P450 (CYP2B enzymes) in animals and also guinea pigs possess much higher activity to metabolize CB180 than rats and hamsters.

Distribution and excretion of 2,2',3,4',5,5',6-heptachlorobiphenyl (CB187) and its metabolites in rats and guinea pigs.

4-Hydroxy (OH)-2,2',3,4',5,5',6-heptachlorobiphenyl (CB187) is a polychlorinated biphenyl (PCB) metabolite present in human serum at the highest concentration of the PCB metabolites. Our previous study demonstrated that CB187 was metabolized by rat and guinea pig liver microsomes to the major metabolite 4'-OH-2,2',3,3',5,5',6-heptachlorobiphenyl (CB178), and the two minor metabolites 4-OH-CB187 and 4'-OH-2,2',3,5,5',6-hexachlorobiphenyl (CB151). In this study, the distribution of these metabolites in serum, liver and kidney, and their fecal excretion, were examined in rats and guinea pigs intraperitoneally dosed with CB187. Similarly to the in vitro study, 4'-OH-CB178 was a major metabolite in the liver, serum and feces of both animal species on day 4 after CB187 injection, and the level in the liver was about 20 times higher in untreated guinea pigs than in untreated rats. In addition, 4-OH-CB187, a minor metabolite, was detected in the serum and kidneys, but not in the feces, of both guinea pigs and rats. Another minor metabolite, 4'-OH-CB151, was detected at a lower level only in guinea pig feces; little was found in the serum or liver of either animals. Over the 30d following CB187 injection into guinea pigs, 4'-OH-CB178 and 4-OH-CB187 in the serum was observed at higher level on day 4 and day 16 after injection, respectively. The majority of the 4'-OH-CB178 was rapidly excreted to the feces following unmetabolized CB187, whereas 4-OH-CB187 was not found in guinea pig feces and liver during 30d. These results support previous reports that 4-OH-CB187 is retained persistently in animal blood.

Uptake of aristolochic acid I into Caco-2 cells by monocarboxylic acid transporters.

The uptake mechanism of aristolochic acid I (AAI) was investigated using Caco-2 cells cultured on dishes and permeable membranes. The uptake of AAI from the apical membrane of Caco-2 cells cultured on a dish was rapid, and a decrease in the pH of the incubation medium significantly increased uptake. Incubation at low temperature (4°C) and treatment with sodium azide (a metabolic inhibitor) or carbonylcyanide p-trifluoromethoxyphenylhydrazone (a protonophore) significantly inhibited the AAI uptake. Coincubation with L-lactic acid or benzoic acid, typical substrates for the proton-linked monocarboxylic acid transporters (MCTs), significantly decreased the AAI uptake, as did coincubation with α-cyano-4-hydroxycinnamate (an inhibitor of MCTs). Dixon plotting revealed the competitive inhibition of benzoic acid on the AAI uptake. To confirm the AAI uptake via MCTs, the apical-to-basolateral transport of AAI was investigated using the Caco-2 cells cultured on the permeable membranes. The transport of AAI at pH 6.0 was markedly higher than that at pH 7.4, and was significantly decreased by coincubation with benzoic acid. These results suggest that the uptake of AAI from the apical membrane of Caco-2 cells is mediated mainly by MCTs along with benzoic acid.

Carrier-mediated uptake of nobiletin, a citrus polymethoxyflavonoid, in human intestinal Caco-2 cells.

The mechanism of intestinal absorption of nobiletin (NBL) was investigated using Caco-2 cells. The uptake of NBL from the apical membranes of Caco-2 cells was rapid and temperature-dependent and the presence of metabolic inhibitors, NaN3 and carbonylcyanide p-trifluoromethoxyphenylhydrazone, did not cause a decrease in NBL uptake. The relationship between the initial uptake of NBL and its concentration was saturable, suggesting the involvement of a carrier-mediated process. The Km and uptake clearance (Vmax/Km) values for NBL were 50.6 and 168.1µl/mg protein/min, respectively. This clearance value was about 9-fold greater than that of the non-saturable uptake clearance (Kd: 18.5µl/mg protein/min). The presence of structurally similar compounds, such as quercetin and luteolin, competitively inhibited NBL uptake. These results suggest that uptake of NBL from the apical membranes of Caco-2 cells is mainly mediated by an energy-independent facilitated diffusion process.

3,3',4,4'-Tetrachlorobiphenyl-mediated decrease of serum thyroxine level in C57BL/6 and DBA/2 mice occurs mainly through enhanced accumulation of thyroxine in the liver.

A single intraperitoneal injection (50 mg/kg) of 3,3',4,4'-tetrachlorobiphenyl (CB77), a 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-type polychlorinated biphenyl, led to significant decreases in the levels of serum total thyroxine (T4) and free T4 without increase in the level of serum thyroid-stimulating hormone at 7 d later in both TCDD-sensitive C57BL/6 and TCDD-resistant DBA/2 mice. When [(125)I]T4 was injected into the mice 7 d after treatment with CB77, the levels of biliary [(125)I]T4 and [(125)I]T4-glucuronide increased 90 to 120 min post injection in C57BL/6 mice, but not in DBA/2 mice, compared with levels in the corresponding control mice. In contrast, in both strains of mice, the CB77-pretreatment led to similar changes in the levels of the [(125)I]T4 bound to the serum transthyretin, albumin, and thyroxine-binding globulin. Consequently, treatment with CB77 promoted the clearance of [(125)I]T4 from the serum and further raised the steady-state volumes of distribution of [(125)I]T4, the concentration ratio (Kp value) of the liver to the serum, and the distribution of [(125)I]T4 in the liver in both strains of mice. The present findings indicate that in mice, the CB77-mediated decrease in the serum T4 level occurs through enhanced accumulation of hepatic T4 rather than through increased activity of hepatic thyroxine-uridine 5'-diphosphate-glucuronosyltransferase(s).

[Species difference in the metabolism of 2, 2', 3, 4', 5, 5'-hexachlorobiphenyl (CB146) by animal and human liver microsomes].

The in vitro metabolism of 2, 2', 3, 4', 5, 5'-hexachlorobiphenyl (hexaCB) (CB146) was examined using liver microsomes of rats, guinea pigs, hamsters and human. Untreated animal livers produced one metabolite (M-2) in rats, three metabolites (M-l, M-2and M-3) in guinea pigs and no metabolite in hamsters. Pretreatment of phenobarbital (PB) resulted in a marked increase of M-1 in three animals and of M-2in guinea pigs. In contrast, pretreatment of 3-methylcholanthrene showed a significant increase of M-3 in guinea pigs and a decrease of M-2in rats. Human liver microsomes prepared from nine Caucasians mainly formed M-2and M-3 at a ratio of 2: 1 and two individuals also formed one more metabolite M-1. The formation of M-1 was significantly correlated with CYP2B6 activity. By comparison of the GC-MS data of three metabolites with synthesized authentic samples, M-1 and M-2were determined to be 3'-hydroxy (OH)-CB146 and 4-OH-CB146, respectively. However, M-3 is unclear at present except the fact that it is OH-hexaCB. These results suggest that 3'-OH-CB146 is formed by PB-inducible cytochrome P450 (CYP2B enzymes) in animal and human livers and 4-OH-CB146 is a major metabolite in rat and human liver.

A possible mechanism for 2,3',4,4',5'-pentachlorobiphenyl-mediated decrease in serum thyroxine level in mice.

The effect of 2,3',4,4',5'-pentachlorobiphenyl (CB118) on serum total thyroxine (T4) level was comparatively examined between C57BL/6 and DBA/2 mice, which are sensitive and insensitive, respectively, to aryl hydrocarbon receptor-mediated biological changes. After 5 d of CB118 administration (50 mg/kg, intraperitoneally (i.p.)), the serum total T4 levels in both strains of mice were markedly decreased. However, significant decreases in serum thyroid-stimulating hormone levels were observed in DBA/2 mice, but not in C57BL/6 mice. In contrast, significant increases in the level and activity of hepatic T4-uridine 5'-diphosphate (UDP)-glucuronosyltransferase by CB118 treatment were observed only in C57BL/6 mice. Likewise, significant increases in the amounts of biliary [(125)I]T4 and [(125)I]T4-glucuronide after injection of [(125)I]T4 were observed only in the CB118-pretreated C57BL/6 mice. The CB118-mediated changes in the levels of [(125)I]T4 bound to transthyretin (TTR), albumin, and thyroxine binding globulin (TBG) were also observed in C57BL/6 mice, but not in DBA/2 mice. Despite such strain differences, significant increases in the liver-selective accumulation of [(125)I]T4 by CB118-pretreatment was observed in both C57BL/6 and DBA/2 mice. The present findings indicate that CB118-mediated decreases in levels of serum T4 in C57BL/6 and DBA/2 mice occur mainly through enhanced accumulation of hepatic T4.

Levels of mercury in muscle and liver of star-spotted dogfish (Mustelus manazo) from the northern region of Japan: a comparison with spiny dogfish (Squalus acanthias).

We analyzed mercury (Hg) concentrations in muscle and liver samples of star-spotted dogfish (Mustelus manazo) caught off the northern region of Japan and compared them with those of spiny dogfish (Squalus acanthias) caught in the same region. The average body length of male star-spotted dogfish specimens was significantly smaller than that of female specimens, reflecting the slower growth rate of male fish. Hg concentrations in liver and muscle increased with increases in body length and estimated age of both male and female star-spotted dogfish specimens. However, the relationships between Hg concentration in liver or muscle and body length or estimated age of male specimens differed markedly from those of female specimens, reflecting differences in growth rate and cessation of growth on reaching maturity. Marked increases in Hg concentration in liver of male and female star-spotted dogfish specimens were observed slightly later than increases in Hg concentration in muscle of those specimens due to growth cessation. These marked increases in Hg in liver may reflect increases in Hg due to the formation of mercury selenide. Similar results were previously reported in spiny dogfish specimens, except spiny dogfish showed only trace levels of Hg in liver (Endo et al., Chemosphere 77:1333-1337, 2009). The greater lipid content in liver and the larger liver size in spiny dogfish may explain the much lower levels of Hg observed in liver of spiny dogfish compared with those in the star-spotted dogfish.

Comparative study on 2,2',4,5,5'-pentachlorobiphenyl-mediated decrease in serum thyroxine level between C57BL/6 and its transthyretin-deficient mice.

The relationships between the changes in the levels of serum total thyroxine (T(4)), serum T(4)-transthyretin (TTR) complex, and accumulation of T(4) in tissues by 2,2',4,5,5'-pentachlorobiphenyl (PentaCB) were examined using wild-type C57BL/6 (WT) and its TTR-deficient (TTR-null) mice. The constitutive level of serum total T(4) was much higher in WT mice than in TTR-null mice. In WT mice 4 days after a single intraperitoneal injection with PentaCB (112 mg/kg), serum total T(4) level was significantly decreased along with a decrease in serum T(4)-TTR complex, and the levels of serum total T(4) in the PentaCB-treated WT mice were almost the same to those in PentaCB-untreated (control) TTR-null mice. In addition, a slight decrease in serum total T(4) by PentaCB treatment was observed in TTR-null mice. Furthermore, clearance of [(125)I]T(4) from the serum after [(125)I]T(4)-administration was promoted by the PentaCB-pretreatment in either strain of mice, especially WT mice. On the other hand, accumulation level of [(125)I]T(4) in the liver, but not in extrahepatic tissues, was strikingly enhanced in the PentaCB-pretreated WT and TTR-null mice. Furthermore, in both strains of mice, PentaCB-pretreatment led to significant increases in the steady-state distribution volume of [(125)I]T(4) and the concentration ratio of the liver to serum. The present findings demonstrate that PentaCB-mediated decrease in serum T(4) level occurs mainly through increase in accumulation level of T(4) in the liver and further indicate that the increased accumulation of T(4) in the liver of WT mice is primarily dependent on the PentaCB-mediated inhibition of serum T(4)-TTR complex formation.

Marine sponge: a potential source for methoxylated polybrominated diphenyl ethers in the Asia-Pacific food web.

Marine sponges collected in Palau, Micronesia, were investigated for hydroxylated or methoxylated analogues of brominated diphenyl ethers (BDEs), brominated dibenzo-p-dioxin (BDD), and brominated biphenyls. The neutral fractions of Haliclona sp. and Callyspongia sp. contained 2'-methoxy-2,3',4,5'-tetraBDE, 6-methoxy-2,2',4,4'-tetraBDE, 2',6-dimethoxy-2,3',4,5-tetraBDE 2,2'-dimethoxy-3,3',5,5'-tetrabromobiphenyl, several methoxy-triBDEs, and dimethoxy-penta-/hexaBDEs. The methoxylated BDEs in sponges were strikingly similar to those of local fish living in the western Pacific Ocean. The total concentrations of these compounds (ΣMeO-PBDE) in both sponges were 63.5 µg/g extractable organic matter (EOM) for Haliclona sp. and 36.5 µg/g EOM for Callyspongia sp., which were about 2 orders of magnitude higher than the levels seen in tropical coral reef fish (unicornfish or surgeonfish) (280-290 ng/g lipid) and groupers (550 ng/g lipid) from Okinawan coastal waters. The phenolic fractions of both sponges contained hydroxy-methoxy tetra-/pentaBDEs as well as hydroxy-tetraBDD, in addition to the corresponding phenolic tetraBDE analogues. Although the total concentrations of phenolic products (27-80 µg/g EOM) in both sponges fell within a range comparable to the methoxylated products, ΣOH-PBDE in local fish were trace level (less than 10 ng/g lipid of) or undetectable. This survey indicates that marine sponges are a possible source of the MeO-PBDE analogues that biomagnify via the food chain to the higher trophic organisms in the western Pacific, whereas the distribution of the corresponding hydroxylated analogues is limited.