Negative correlation between plasma thyroid hormone levels and chlorinated hydrocarbon levels accumulated in seals from the coast of Hokkaido, Japan

Abstract

Chlorinated hydrocarbon (CHC) levels in the blubber of larga seals (Phoca largha) and ribbon seals (Phoca fasciata) collected from the coastal waters of Hokkaido, Japan, were determined in order to assess the hormonal effects of CHC exposure in free-ranging pinnipeds. Plasma thyroid hormone levels, including total thyroxine (T4), free thyroxine (free T4), total triiodothyronine (T3), and free triiodothyronine (free T3), were also measured. Higher concentrations of polychlorinated biphenyl congeners (PCBs), dichlorodiphenyltrichloroethane and its metabolites, and chlordane compounds were found in the range of 380 to 2,600 ng/g, 350 to 2,600 ng/g, and 120 to 760 ng/g on a wet-weight basis, respectively. Spearman rank correlation analyses showed that in larga seals, plasma total T3 and free T3 levels negatively correlated with levels of all the CHCs analyzed, although there was no such correlation between total or free T4 levels and CHC concentrations. In ribbon seals, total T3 levels significantly decreased with an increase of di-ortho PCB (PCB170 and 180) residues. These findings indicated that the plasma T3 deficiency could be associated with some CHC exposure in larga and ribbon seals and that the responses of plasma thyroid hormones may be useful biomarkers for CHC exposure in ribbon seals.

Thyroid hormone status in gray seal (Halichoerus grypus) pups from the baltic sea and the atlantic ocean in relation to organochlorine pollutants

“…Negative correlations between OCs and plasma T3 concentrations in gray seal pups of the present study are consistent with observations in Larga seals (Phoca larga) from Japanese waters, where plasma TT3 and FT3 concentrations correlated negatively with blubber PCB concentrations [9]. In ribbon seals (Phoca fasicata), also from Japanese waters, plasma TT3 levels decreased significantly with increased blubber PCB concentrations, whereas no such relationship was found between blubber PCBs and FT3 in this species [9]. Plasma TT4 and FT4 concentrations, however, were not affected by blubber PCB concentrations in either Larga or ribbon seals [9].…”

“…Numerous studies have documented that OCs may affect thyroid hormone (TH) function and homeostasis in experimental animals, wildlife species, and humans (as reviewed in [1][2][3]). Several studies indicate that OCs also may affect TH function in seals [7][8][9][10][11].…”

Endocrine-Disrupting Chemicals and Climate Change: A Worst-Case Combination for Arctic Marine Mammals and Seabirds?

“…Because many of these species also inhabit Arctic waters, I have chosen to include some of the main findings from these studies here. In ribbon seals ( Phoca fasicata ) from Japanese waters, TT 3 levels decreased significantly with increased blubber concentrations of PCB-170 and PCB-180, whereas no such relationship was found between blubber PCBs and FT 3 (Chiba et al 2001). In Larga seals ( Phoca largha ), also from Japanese waters, plasma TT 3 and FT 3 correlated negatively with blubber PCB concentrations, whereas no such relationships were found between blubber PCB concentrations and TT 4 and FT 4 in either Larga or ribbon seals (Chiba et al 2001).…”

Investigations of Thyroid and Stress Hormones in Free-Ranging and Captive Harbor Porpoises (Phocoena phocoena): A Pilot Study

“…Organochlorines like polychlorinated biphenyls (PCBs); p,p'-dichlorodiphenyltrichloroethane (p,p'-DDT); and its metabolite, p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE) are part of a wide range of environmental contaminants suspected to interfere with endocrine functions in marine mammals (Aguilar & Borrel, 1995;Bruhn et al, 1995;Brouwer et al, 1999;Gregory & Cyr, 2003). Studies performed on laboratory and domestic animals as well as marine mammals showed a correlation between the intake of organochlorines and changes in hormone levels (Byrne et al, 1987;Brouwer et al, 1989;Chiba et al, 2001;Skaare et al, 2001;Haave et al, 2003;Braathen et al, 2004;Oskam et al, 2004;Sørmo et al, 2005;Zimmer et al, 2009). Organochlorines are lipophilic compounds.…”