Contaminant‐related disruption of vitamin a dynamics in free‐ranging harbor seal (Phoca vitulina) pups from british columbia, canada, and washington state, usa

Abstract

Abstract-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.

Accumulation of dietary organochlorines and vitamins in Baltic seals

“…The elevated level of plasma retinol in the Baltic grey seals, reported previously, would further support this hypothesis (Nyman et al, 2003). These elevated plasma retinol levels are caused by POPs mobilising vitamin A stores from liver (Simms, Jeffries, Ikonomou, & Ross, 2000). Plasma retinol levels are maintained within a normal range of concentrations as long as there is some minimal level of vitamin A in the liver and in extra-hepatic tissues (Blomhoff, Green, Green, Berg, & Norum, 1991).…”

Fireproof killer whales (Orcinus orca): flame-retardant chemicals and the conservation imperative in the charismatic icon of British Columbia, Canada

“…For example, as observed in some captive feeding and laboratory animal studies, contaminant-associated alterations have been observed in a number of marine mammal populations, including alterations in thyroid hormone and vitamin A (Simms et al 2000;Jenssen et al 2003;Braathen et al 2004), cytochrome P450 enzymes (Nyman et al 2003), and immune function (Lahvis et al 1995;Levin et al 2005). In most cases, confounding factors have been eliminated through study design or by statistical means, but critical evaluation of the "correlation" is needed to ensure that the relationship is causal (Ross et al 2003;Ross 2004).…”

Proliferative Responses of Harbor Seal (Phoca vitulina) T Lymphocytes to Model Marine Pollutants

“…Previous investigations of contaminant-induced immune suppression in marine mammals have typically correlated impaired immune responses or less specific biomarkers with tissue levels of polyhalogenated aromatic hydrocarbons (PHAHs) such as the organochlorine pesticides and PCBs (Reijnders, 1994;Lahvis et al, 1995;Simms et al, 2000). While providing circumstantial evidence for immune suppression, causal relationships and mechanisms of action could not be established.…”