Methylsulfone Polychlorinated Biphenyl and 2,2-Bis(chlorophenyl)-1,1-Dichloroethylene Metabolites in Beluga Whale (Delphinapterus Leucas) From the St. Lawrence River Estuary and Western Hudson Bay, Canada

Abstract

Abstract-Knowledge is limited regarding methylsulfone (MeSO 2 )-polychlorinated biphenyl (PCB), and especially MeSO 2 -2,2-bis(chlorophenyl)-1,1-dichloroethylene (DDE), metabolites in cetacean species. We hypothesized that the ability of beluga whale (Delphinapterus leucas) to biotransform PCB and DDE compounds, and to form and degrade their MeSO 2 -PCB and -DDE metabolites, is related to the capacity for xenobiotic metabolism. Adipose biopsies were collected from male and female beluga whale from distinct populations in the St. Lawrence River estuary (STL) and western Hudson Bay (WHB), Canada, which are contrasted by the exposure to different levels of cytochrome P450 enzyme-inducing, chlorinated hydrocarbon contaminants. The PCBs, DDTs, DDEs, 28 MeSO 2 metabolites of 14 meta-para chlorine-unsubstituted PCBs, and four MeSO 2 metabolites of 4,4Ј-and 2,4Ј-DDE were determined. The mean concentrations of total (⌺-) MeSO 2 -PCB in male STL beluga (230 ng/g), and ratios of ⌺-MeSO 2 -PCB to ⌺-PCB (0.05) and ⌺-precursor-PCB (0.17) were approximately twofold higher, whereas the ⌺-precursor-PCB to ⌺-PCB ratio was approximately twofold lower, than in male WHB beluga. Both populations had a low formation capacity for MeSO 2 -PCBs with Նsix chlorines (Ͻ4% of ⌺-MeSO 2 -PCBs). The congener patterns were dominated by trichloro-and tetrachloro-MeSO 2 -PCBs, and tetrachloro-and pentachloro-MeSO 2 -PCBs in WHB and STL animals, respectively. In addition to 2-and 3-MeSO 2 -4,4Ј-DDE, two unknown MeSO 2 -2,4Ј-DDEs were detected. The mean 3-MeSO 2 -4,4Ј-DDE concentration in STL beluga (1.2 ng/g) was much greater than in WHB (Ͻ0.01 ng/g) animals. The concentrations of 4,4Ј-DDE, and not 3-MeSO 2 -4,4Ј-DDE, increased with age in male STL animals. We demonstrated that sulfone formation and clearance is related to metabolic capacity, and thus PCB, DDE, and MeSO 2 -PCB and -DDE toxicokinetics differ for STL and WHB beluga. In the past, the capacity of odontocetes for PCB and DDE biotransformation leading to persistent sulfone metabolites has been underestimated. More information is needed for other cetacean species and marine mammals. The results of this study indicate that MeSO 2 -PCBs and -DDEs need to be included in the toxicologic risk assessment of PCB and DDT exposure in odontocetes, and perhaps for cetaceans in general.

A reassessment of the nomenclature of polychlorinated biphenyl (PCB) metabolites.

“…CH 3 SO 2 -PCBs are generally referred to as MeSO 2 -PCBs. The numbers of animals and populations where tissue residues of these PCB metabolites have been characterized remains small, but HO-PCBs and MeSO 2 -PCBs are emerging as common contaminant phenomena in wildlife and humans and are of increasing importance in risk assessments of exposure to PCBs (Bennett et al 2002;Campbell et al 2003;Chu et al 2002Chu et al , 2003Guvenius et al 2002;Hoekstra et al 2003;Hovander et al 2002;Letcher et al 2000aLetcher et al , 2000bLi et al 2003;Sandala et al, in press;Sandau et al 2000aSandau et al , 2000bSandau et al , 2002Stapleton et al 2001). In some species and tissues, HO-PCB and MeSO 2 -PCB concentrations may be in a similar or higher range with respect to the concentrations of the parent PCBs.…”

“…In several recent reports, the number of the MeSO 2 -group has been primed or unprimed depending on which phenyl ring this substituent was positioned (Guvenius et al 2002;Hoekstra et al 2003;Letcher et al 2000aLetcher et al , 2000b. Following this revised nomenclature system, 3-MeSO 2 -2,2´,4´,5-tetrachlorobiphenyl is abbreviated to 3´-MeSO 2 -CB49.…”

Distribution of methyl sulfone metabolites of polychlorinated biphenyls and p,p'-DDE in human tissues.

“…Although the major metabolic route is hydroxylation generally followed by excretion, significant amounts of methylsulfonyl metabolites of chlorinated biphenyls (MeSO 2 -CBs) and of DDE (MeSO 2 -DDE) may be accumulated in tissues because of their lipophilic character and specific protein-binding properties (Jönsson et al 1994;Lund et al 1985Lund et al , 1988. MeSO 2 -CBs and MeSO 2 -p,p´-DDE have been mostly quantified in fat and liver tissues (Letcher et al 2000a(Letcher et al , 2000b, whereas hydroxylated PCBs were mostly determined in blood (Letcher et al 2000a).…”

La contamination du béluga de l’estuaire du Saint-Laurent par les polluants organiques persistants en revue

“…Le tableau 1 rapporte distinctement les niveaux de BPC chez les mâles et les femelles. Certaines études rapportent des niveaux moyens (moyennes géométriques) plus élevés chez les mâles (DEVIGNE, 2003;LEBEUF et al, 2007a;MARTINEAU et al, 1997;MUIR et al, 1990MUIR et al, ,1996a alors que d'autres études rapportent des niveaux similaires chez les deux genres (HOBBS et al, 2003;LETCHER et al, 2000b;MUIR et al, 1996b). Les travaux de GAUTHIER et al (1998) Une comparaison sommaire des niveaux moyens de BPC rapportés dans les gras des bélugas de l'ESL, en considérant l'ensemble des études disponibles (Tableau 1), semble indiquer une tendance à la baisse de la contamination au cours des ans.…”