Absorption and ocular deposition of dietary lutein in marine mammals.

Cataracts and ocular disease are common lesions of marine mammals in zoological collections. Lutein, an oxygenated carotenoid, may have therapeutic or prophylactic effects on ocular disorder. Therefore, this study examined the ability of marine mammals to absorb dietary lutein. Two preliminary trials examined lutein in two forms (beadlet or ester) in a small sample size of marine mammals representing pinnipeds and cetaceans. Lutein was fed daily in tablets providing 0.89-3.6 mg lutein/kg body weight(0.75) per day for 15 days to 2 years. A third study was conducted using lutein beadlet fed at 3.6 mg lutein/kg body weight(0.75) per day for 15-21 days. Blood was analyzed for lutein pre- and postsupplementation. In the preliminary trials, lutein beadlet was observed to result in greater blood lutein levels than lutein esters, and cetaceans had more noticeable responses than pinnipeds. In Study 3, serum lutein and zeaxanthin increased postsupplementation in beluga whales (P < 0.05), and serum lutein tended to increase postsupplementation in dolphins (P < 0.10), but little change was seen in serum lutein in pinnipeds or manatee. Opportunistic retinal samples demonstrated some detectable lutein in the retina of a dolphin and several harp seals. The lutein levels in dolphins after supplementation are similar to those reported in free-ranging animals. Ocular lutein in harp seals demonstrates that ocular deposition occurs despite low circulating lutein levels.

Vitamin D metabolism in the hooded seal (Cystophora cristata).

Fish-eating mammals, such as seals, appear to ingest levels of vitamin D that are toxic to most mammals. To determine how seals cope with high vitamin D intakes, the metabolism of tritiated cholecalciferol ([3H]D3) was investigated in hooded seal (Cystophora cristata) pups during their postweaning fast and pups and adults consuming herring alone or supplemented with 400,000 iu D3 daily. [3H]D3 was metabolized to 25-[3H]OHD3 and 24,25-[3H](OH)2D3. 1,25-[3H](OH)2D3 was not detected, but plasma levels of 1,25-(OH)2D were similar to those in other mammals and were not affected by vitamin D intake. Plasma vitamin D, 25-OHD and 24,25-(OH)2D increased with vitamin D intake, but 25-OHD did not increase to the extent seen in other mammals. The supplemented seals showed no evidence of toxicity. Levels of 24,25-(OH)2D were higher in the unsupplemented seals (4 to 33 ng/mL) than reported in other mammals with similar 25-OHD levels and did not decrease with 25-OHD. High levels of 24,25-(OH)2D relative to 25-OHD have also been found in hooded seals in the wild. The half-lives of vitamin D, 25-OHD and 24,25-(OH)2D were shorter than those reported for most other mammals. Increased conversion of 25-OHD to 24,25-(OH)2D and a high capacity for vitamin D storage in their large blubber mass appeared to be factors in the resistance of seals to vitamin D toxicity.

Pollutants in harp seals (Phoca groenlandica). II. Heavy metals and selenium.

Between 1976 and 1978, 249 harp seals were sampled from five locations in the Northwest Atlantic and Arctic for heavy metal and selenium residue analyses in tissue. Significant loading was apparent only in blood, brain, kidney, liver and muscle. Samples were analysed for mercury (Hg), selenium (Se), copper (Cu), cadmium (Cd) and lead (Pb). The seals carried higher levels of Cd than of the other metals. Residue levels of Cd were highest in kidney tissue; levels of other metals were highest in liver. Both males and females bioaccumulated Cd, Hg and Se. Cd, Hg, Se and Cu residues were detected in tissue from neonatal seals, indicating that transplacental and transmammary transfer of these elements had occurred. Despite the passage of residues from mother to pup, females bore significantly higher levels of Hg and Cd than males. Conversely, levels of Cu, Se or Pb did not appear to differ significantly between sexes. There was considerable individual variation in residue levels. This, coupled with the extensive annual migration undergone by these animals, made it difficult to arrive at definite conclusions regarding geographic accumulation patterns.

Hydrocarbon metabolism and cortisol balance in oil-exposed ringed seals, Phoca hispida.

1. Ringed seals were exposed experimentally to oil contamination, by feeding of a [14C]naphthalene marked crude oil in fish for up to 4 days at a rate of 5 ml/day. 2. Mixed function oxygenase (MFO) activity, measured as aryl hydrocarbon hydroxylase in liver and kidney, was found to be induced, in particular in kidney tissue where the activity increased 3-fold. 3. MFO induction correlated with a high degree of conversion of crude oil hydrocarbons to water-soluble metabolites. Most of the radioactivity was found in the polar fraction of plasma and urine. 4. Plasma cortisol levels were somewhat elevated by captive holding, and increased markedly after oil-exposure. Cortisol half-life decreased after oil exposure from 1 3/4 to 1 hr.

Mercury and selenium content and chemical form in human and animal tissue.

The content, chemical form, and distribution of mercury and selenium were determined for selected samples of human and animal tissue by gas chromatography. Methylmercury averaged 38.7% of the total mercury content in homogenized human brain. For human heart, spleen, liver, kidney and placenta, methylmercury comprised 40.2%, 57.0%, 39.6%, 6.0% and 57.1% respectively, of the total mercury content. Similar results were obtained for the heart and liver of a whitetail deer. Methylmercury represented 9.1%, 62.9% and 24.1% of the total mercury content in seal liver, seal meat and deer meat, respectively. For all samples, a significant portion of the total selenium content, averaging 27%, was present as selenate (Se VI). Tissue selenium content did not correlate with the corresponding mercury content. In brain, heart and placenta, and in seal liver and meat, 53% to 80% of the total mercury content was water-extractable. For human kidney, liver and spleen, and deer meat, only 15% to 45% of the total mercury was extractable. On a percentage basis, inorganic mercury was more extractable than methylmercury, except for human kidney and liver, and deer meat. For all samples, except kidney, liver and deer meat, 55% to 76% of the total selenium content was water-extractable, Se VI being more extractable on a percentage basis than selenite (Se IV) and selenide (Se-II).

Occurrence and fate of organic and inorganic contaminants in marine animals.

Most chemical contaminants occur in highest concentrations in coastal waters, often maximized in very localized areas. In general, this situation represents the exposure pattern for marine animals. However, the availability of contaminant to an organism depends not only on its concentration but also on its chemical nature, its physical state, and whether the source of exposure is the surrounding seawater or the diet. Depending on the type of exposure, uptake occurs across absorptive surfaces, such as those of the respiratory apparatus or gastrointestinal tract, where selectivity may occur, even among neighboring homologs. Deposition in tissues, accumulation, degradation, or depuration depends on tissue type, metabolic processes, detoxification mechanisms, and the adaptive status of a particular animal. This hypothesis is examined briefly for hydrocarbons, pesticides, other miscellaneous organic contaminants, heavy metals, and radionuclides. It is concluded that most data relate to occurrence and distribution. Considerably less information is available on the underlying biochemical processes.

A study of the effects of methyl mercury, cadmium, arsenic, selenium, and a PCB, (Aroclor 1254) on adrenal and testicular steroidogeneses in vitro, by the gray seal Halichoerus grypus.

An in vitro study on the effects of the contaminants polychlorinated biphenyl (Aroclor 1254) (PCB), methyl mercury (MeHg), arsenic (As), cadmium (Cd), and selenium (Se) on the biosynthesis of steroid hormones in the gray seal (Halichoerus grypus) indicated altered steroid biosynthesis. Biotransformed delta4-androstene-3, 17-dione (delta 4A), dehydroepiandrosterone, 11-ketotestosterone (11-KT), and testosterone (T) were detected in all seal testicular incubates. Yields of 11-KT were greatly increased in the presence of Aroclor 1254. All contaminants except As and Se stimulated the in vitro biosyntheses of T, with the greatest increase in production of T being in the Cd-treated tissue. Cortisol (F), corticosterone (B), aldosterone (ALDO) but no cortisone (E), were biosynthesized by the seal adrenal tissue. Corticosterone (B) was the principal transformation product in all incubations with less B produced by the treated adrenals than by the control. The lowest yeild of B was achieved by the Se-treated adrenal. The yeild of ALDO was also lower in all contaminant treated incubations, with Se and Cd giving the greatest inhibition. More F was biosynthesized by all the treated adrenals than by the control. The greatest increase of production of F(6-fold) from progesterone was by the As-treated adrenal.

Mercury and selenium in marine mammals and birds.

Information is provided concerning the concentrations of mercury and selenium in tissues of marine animals. In marine mammals a 1:1 Hg/Se molecular increment ratio was found and an almost perfect linear correlation between mercury and selenium. It is suggested that marine mammals are able to detoxify methylmercury by a specific chemical mechanism in which selenium is involved. The results also indicate that the fate of methylmercury in fish-eating marine birds differs fundamentally from that in marine mammals.