Effects of polychlorobiphenyls, polybromodiphenylethers, organochlorine pesticides and their metabolites on vitamin A status in lactating grey seals (original) (raw)
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Aquatic Toxicology, 2007
Polychlorinated biphenyls (PCBs) have been associated with a number of toxic effects in marine mammals such as endocrine disruption and immunotoxicity that, in turn, are widely thought to have contributed to population level impacts including reproductive failure and outbreaks of disease. In this study, the dietary hormone vitamin A and expression levels of one of its receptors, retinoic acid receptor ␣ (RAR␣), were used as biomarkers of PCB-associated health effects in harbour seals. Harbour seal pups (n = 24) were live-captured in coastal British Columbia, Canada, and Washington State, USA, and sampled for whole blood (to obtain peripheral blood mononuclear cells, PBMCs) and blood plasma, as well as biopsies of blubber and skin. Concentrations of circulatory vitamin A (retinol) in plasma and stored vitamin A in blubber were negatively associated with blubber PCB concentrations (R = −0.518, p = 0.013 and R = −0.645, p = 0.009, respectively). However, vitamin A concentrations in skin, an important target tissue, remained constant, which likely reflects a compensatory transfer from blubber to maintain physiological functions. In addition, we characterized the harbour seal RAR␣, and investigated its expression levels as a potential biomarker in seals. RAR␣ expression in blubber, but not on PBMCs, was elevated in more contaminated animals (R = 0.580, p = 0.009). This may represent a direct contaminant-related effect, or, a compensation for the contaminant-related disruption of (circulatory and/or blubber) hormone levels. Since vitamin A is critical to developmental, reproductive and immunological health, our observations of a contaminant-related disruption of its physiology in free-ranging seals may portend population level consequences. Vitamin A concentrations and RAR␣ expression levels can therefore represent relevant and sensitive biomarkers of PCB-associated toxic effects in toxicological studies of marine mammals.
Relationships between vitamin A and PCBs in grey seal mothers and pups during lactation
Environmental Pollution, 2010
A previous study has shown a simultaneous increase of vitamin A and PCBs in grey seal (Halichoerus grypus) milk at late lactation . Here we sought to understand this unexpected relationship by comparing the dynamics of vitamin A and PCBs in the different tissue compartments of transfer. Lactating grey seals and their pups were sampled longitudinally in Scotland during the 2006 breeding season. As blubber reserves decreased, concentrations of vitamin A and PCBs increased during lactation in the inner layer of maternal blubber. A concomitant rise was observed in milk and consequently in the serum of suckling pups. The similar dynamics of vitamin A and PCBs in milk and inner blubber suggest a common mechanism of mobilisation from maternal body stores and transfer into the milk. A panel data analysis highlighted a negative impact of PCBs in milk and pup serum on vitamin A status in pup serum.
Environmental Toxicology and Chemistry, 2000
Marine mammals can bioaccumulate high concentrations of lipophilic environmental contaminants, such as polychlorinated biphenyls (PCBs), polychlorinated dibenzo-para-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs), through the diet. Both laboratory and wildlife studies have shown that these persistent chemicals can disrupt the regulation of vitamin A (retinol), a dietary hormone required for immune function, reproduction, growth, and development. To determine whether environmental contaminants affect the circulatory vitamin A dynamics of free-ranging harbor seals (Phoca vitulina), we live-captured 61 pups from British Columbia, Canada, and Washington State, USA, and obtained blood and blubber biopsy samples. Harbor seal pups from Washington State were six times more contaminated with total PCBs than pups from British Columbia and had significantly lower circulatory retinol levels. However, when data were corrected for differences in nursing status and analyzed as ungrouped sets of data, circulatory retinol levels were positively correlated with contaminant levels in the blubber of nonnursing pups. This increase in retinol may have resulted from a mobilization of liver vitamin A stores into circulation following exposure to milkderived contaminants; this has been observed in laboratory animals exposed experimentally. The contaminant-related disruption of vitamin A dynamics observed in our study occurs at a time when vitamin A is required for growth and development.
Aquatic Toxicology, 2013
We evaluated the utility of vitamin A and E profiles as biomarkers of contaminant exposure in beluga whales (Delphinapterus leucas; n = 66) harvested by the Inuvialuit in the Beaufort Sea. Blubber was an important repository for these vitamins, accounting for 76.8 ± 2.6% of the total body store of vitamin A, and 98.5 ± 0.4% of total vitamin E. While the free alcohol form of vitamin A (retinol) appeared highly regulated, the vitamin A esters were influenced by several biological factors including age, body condition and length. Vitamin E concentrations in liver and blubber were related to age, condition, length and feeding ecology, as described ␦ 15 N and ␦ 13 C. Despite the influence of these factors, collective results from univariate statistics, best fit multiple regressions, and principal component analysis (PCA) identified polychlorinated biphenyls (PCBs) as important determinants of vitamin concentrations and profiles in beluga tissues. Blubber PCB concentrations best explained variation of the first principal component in a PCA of hepatic vitamins (r 2 = 0.13, p = 0.014), and regression models found that vitamin A concentrations were negatively correlated with PCB levels in liver (esters: r 2 = 0.19, p = 0.001), but positively in plasma (retinol: r 2 = 0.20, p = 0.06) and blubber (retinol: r 2 = 0.22, p = 0.001, esters: r 2 = 0.43, p < 0.001). Our analyses provide a basis to propose an integrated toxicity reference value for disruption of vitamin A and E profiles in beluga of 1.6 mg/kg lw PCBs. This disruption of vitamin profiles by moderate levels of PCBs in an arctic cetacean highlights the global reach and impact of these legacy chemicals decades after their peak use.
Environmental Pollution, 2005
Top-trophic predators like California sea lions bioaccumulate high levels of persistent fat-soluble pollutants that may provoke physiological impairments such as endocrine or vitamins A and E disruption. We measured circulating levels of polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT) in 12 healthy juvenile California sea lions captured on An˜o Nuevo Island, California, in 2002. We investigated the relationship between the contamination by PCBs and DDT and the circulating levels of vitamins A and E and thyroid hormones (thyroxine, T4 and triiodothyronine, T3). Serum concentrations of total PCBs (P PCBs) and total DDT were 14 G 9 mg/kg and 28 G 19 mg/kg lipid weight, respectively. PCB toxic equivalents (P PCB TEQs) were 320 G 170 ng/kg lipid weight. Concentrations of P PCBs and P PCB TEQs in serum lipids were negatively correlated (p ! 0.05) with serum vitamin A and T3, potentially reflecting PCB-related toxicity. A slight but not significant negative correlation (p ! 0.1) was observed between serum T4 and the levels of P PCBs and P PCB TEQs. Conversely, no relationship was evident between the contaminant concentrations and vitamin E (p O 0.1). As juvenile California sea lions are useful sentinels of coastal contamination, the high levels encountered in their serum is cause for concern about the ecosystem health of the area.
Environment International, 2009
Harbour seals (Phoca vitulina) and harbour porpoises (Phocoena phocoena) are top predators in the North Sea and consequently accumulate a variety of pollutants in their tissues. Concentrations of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and their hydroxylated metabolites (HO-PCBs and HO-PBDEs) were measured in serum of wild harbour seals (n = 47) and captive harbour porpoises (n = 21). Both species exhibit long life spans and do not have extreme situations, such as complete fasting during periods of lactation, in their annual cycles. For PCBs, concentrations in adult males were slightly higher than in juveniles and lowest in juvenile females. For PBDEs, juveniles have higher levels than adult males and females, probably as a consequence of lactational transfer. However, differences between these age-gender groups were not statistical significant, indicating that individual variation was limited within each species, even without knowing the feeding status of the animals. Body condition, particularly emaciation, has a major influence on the levels of chlorinated and brominated contaminants in serum. Profiles of PCBs were CB 153 N CB 138 N CB 187 N CB 180 and CB 153 N CB 138 N CB 149 N CB 187 N CB 180 for harbour seals and porpoises respectively. For PBDEs, BDE 47 was the predominant congener followed by BDE 100 and 99 in both species. In harbour seals, concentrations of sum PCBs (median: 39,200 pg/ml) were more than 200 times higher than levels of sum PBDEs (median: 130 pg/ml) and almost 10 times higher than concentrations of sum HO-PCBs (4350 pg/ml). In harbour porpoises, concentrations of sum PCBs (median: 24,300 pg/ml) were about 20 times higher than concentrations of PBDEs (median: 1300 pg/ml). HO-PCBs were detected in only 4 harbour porpoises and this at very low concentrations. Naturally-produced MeO-PBDEs were only found in harbour porpoises at concentrations ranging from 120 to 810 pg/ml. HO-PBDEs were not found in any species. In general, harbour seals accumulate less compounds and have mostly lower concentrations than harbour porpoises possibly as a result of a better developed metabolism.
BONE-RELATED EFFECTS OF CONTAMINANTS IN SEALS MAY BE ASSOCIATED WITH VITAMIN D AND THYROID HORMONES
Environmental Toxicology and Chemistry, 2008
The high levels of polychlorinated biphenyls (PCBs) and DDT in gray seal (Halichoerus grypus) and ringed seal (Phoca hispida botnica) in the Baltic Sea have been associated with pathological disruptions, including bone lesions and reproductive failures. The underlying environmental and toxicological mechanisms leading to these pathological changes are not yet fully understood. The present study investigated the relationship between the individual contaminant load and bone-and thyroid-related effects in adult gray seals (n ϭ 30) and ringed seals (n ϭ 46) in the highly contaminated Baltic Sea and in reference areas (Sable Island, Canada, and Svalbard, Norway). In the gray seals, multivariate and correlation analyses revealed a clear relationship between circulating 1,25-dihydroxyvitamin D 3 (1,25(OH) 2 D), calcium, phosphate, and thyroid hormone (TH) levels and hepatic PCB and DDT load, which suggests contaminant-mediated disruption of the bone and thyroid homeostasis. Contaminants may depress 1,25(OH) 2 D levels or lead to hyperthyroidism, which may cause bone resorption. In the ringed seals, associations between circulating 1,25(OH) 2 D, THs, and hepatic contaminants were less prominent. These results suggest that bone lesions observed in the Baltic gray seals may be associated with contaminant-mediated vitamin D and thyroid disruption.
Environmental research, 2016
Pilot whales (Globicephala melas) from the Faroe Islands, North-East Atlantic, have high body concentrations of organohalogenated compounds (OHCs), such as polychlorinated biphenyls (PCBs), organochlorinated pesticides (OCPs) and brominated flame retardants (BFRs). The aim of the present study was to examine if and to what extent blood plasma and liver concentrations of several groups of these OHCs are related to concentrations of relevant nutritional and hormonal biomarkers in pilot whales. Thyroid hormones (THs: total and free thyroxine and total and free triiodothyronine) and vitamin A (retinol), D (25-hydroxyvitamin D3) and E (α-tocopherol) were analysed in plasma (n=27) and vitamin A (total vitamin A, retinol and retinyl palmitate) and E (α- and γ-tocopherol) were analysed in liver (n=37) of Faroe Island pilot whales. Correlative relationships between the biomarkers and OHC concentrations previously analysed in the same tissues in these individuals were studied. The TH concentr...
Environment International, 2012
Twenty grey seal (Halichoerus grypus) mother-pup pairs from the colony of the Isle of May (Scotland) were sampled at early and late lactation in order to study the transfer of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and their metabolites (HO-PCBs and HO-PBDEs) as well as organochlorine pesticides (OCPs), such as DDT and metabolites (DDXs) and hexachlorobenzene (HCB). The transfer of the naturally produced MeO-PBDEs was also investigated. Generally, concentrations (on a lipid weight basis) of the sum of PCBs, PBDEs and DDXs tended to be higher in all tissues at late lactation (for maternal outer blubber ΣPCBs = 3860 ± 2091 ng/g, ΣPBDEs = 120 ± 74 ng/g and ΣDDXs = 559 ± 207 ng/g; for maternal inner blubber ΣPCBs = 4229 ± 3274 ng/g, ΣPBDEs = 148 ± 118 ng/g and ΣDDXs = 704 ± 353 ng/g; for maternal serum ΣPCBs = 1271 ± 796 ng/g, ΣPBDEs = 27 ± 16 ng/g and ΣDDXs = 242 ± 125 ng/g; for milk ΣPCBs = 1190 ± 747 ng/g, ΣPBDEs = 55 ± 36 ng/g and ΣDDXs = 357 ± 160 ng/g; for pup serum ΣPCBs = 1451 ± 901 ng/g, ΣPBDEs = 48 ± 31 ng/g and ΣDDXs = 395 ± 201 ng/g). In all tissues, ΣMeO-PBDEs were found at very low levels or even undetected and their concentrations appeared to increase at late lactation only in maternal inner blubber (2.7 ± 1.3 to 5.3 ± 2.9 ng/g for early and late lactation, respectively) and milk (0.6 ± 0.3 to 1.1 ± 0.5 ng/g for early and late lactation, respectively). The transfer from inner blubber to maternal serum was selective and strongly depended on the log K ow value of the compounds, with less lipophilic compounds being more efficiently released. Only a limited amount of HO-PCBs was transferred during lactation as 4-HO-CB-107 was the only metabolite detected in milk (29 to 40 pg/g lw). On the contrary, most of HO-PCB metabolites found in maternal serum were also detected in pup serum. These findings suggest not only a transplacental transfer of HO-PCBs from mothers to pups but also the possibility of endogenous biotransformation in suckling pups or accumulation of undetectable low amounts from milk.