Fate of chlorinated fatty acids in migrating sockeye salmon and their transfer to arctic grayling

To investigate whether biotransport constitutes an entry route into pristine ecosystems for nonpersistent, nonvolatile xenobiotic compounds, extractable organically bound halogen in sockeye salmon (Oncorhynchus nerka) from Alaska was determined before and after spawning migration. The major organohalogen compounds in the salmon were halogenated fatty acids, predominantly chlorinated species that accounted for up to 35% of the extractable, organically bound chlorine (EOCl) in the fish tissues. The amount of chlorinated fatty acids in the salmon muscle decreased as a result of spawning migration. The decrease was correlated with that of triacylglycerols in the salmon muscle, indicating the chlorinated fatty acids to be mobilized and metabolized to approximately the same extent as the other fatty acids. Chlorinated fatty acids were also transferred to the maturing roe in a manner similar to that of the unchlorinated fatty acids. Lipids of the Arctic grayling (Thymallus arcticus), a fish resident to the spawning lake of the salmon, contained higher concentrations of chlorinated fatty acids than grayling in a lake without migratory salmon. This may reflect a food-chain transfer of the chlorinated fatty acids originating from the salmon, demonstrating a long-range transport route for this type of pollutants to pristine areas.

Structural characterization of 5,6-dichlorotetradecanoic acid, an isolated metabolite of 9,10-dichlorooctadecanoic acid, by studying picolinyl esters, pyrrolidides and methyl esters with electron ionization mass spectrometry

A method is presented for identification of positional isomers of dichlorinated fatty acids, based on derivatization to picolinyl esters prior to gas chromatographic/mass spectrometric analysis in the electron ionization mode. The mass spectra of the picolinyl esters showed structure-specific fragmentation patterns. By using the picolinyl ester, 5,6-dichlorotetradecanoic acid was identified as a metabolite from a cell-culture medium obtained by culturing human cell lines in media supplemented with threo-9,10-dichlorooctadecanoic acid. This indicates that dichlorinated fatty acids are degraded by beta-oxidation. It is also possible to locate tentatively the position of chlorine atoms in 5,6-dichlorotetradecanoic acid as its methyl ester or pyrrolidide.

Subchronic toxicity of Baltic herring oil and its fractions in the rat I: Fractionation and levels of organohalogen pollutants

Baltic herring (Clupea harengus) oil was extracted and fractionated. To examine the contribution to toxicity and biological effects of different halogenated organic pollutants, the herring oil and the fractions were mixed into pelleted food and given to Sprague-Dawley female rats at three levels, corresponding to a human intake of 1.6, 8.2 and 34.4 kg fish per week. Herring oil, its fractions, as well as liver tissues from exposed rats, were analyzed for: eight chlorinated biphenyls, all 2,3,7,8-substituted chlorinated dibenzo-p-dioxins and dibenzofurans, hexachlorocyclohexanes, hexachlorobenzene, 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT), DDT-metabolites, three brominated diphenylethers as well as extractable organically bound chlorine and halogenated fatty acids. A bioassay (EROD) was used for measuring the dioxin-like enzyme induction activity. Nordic Sea lodda (Mallotus villosus) oil was used as a nutritionally equivalent control, with much lower levels of halogenated organic pollutants. A full toxicological subchronic examination is reported in the following paper (Stern et al. 2002). In this study, we report that the fractionation procedure resulted in a substantial reduction of most of the pollutants in the triacylglycerol fraction, and a pronounced enrichment of most of the pollutants into the two other fractions. However, all contaminants were present at some levels in all of the fractions. The concentrations of organohalogens found in this study were representative for Baltic herring during the mid-1990s. Rat liver tissue showed similar residue patterns as the diet, with the exception of chlorinated dibenzo-p-dioxin and dibenzofuran congeners that had a higher liver retention than pesticides, chlorinated biphenyls and brominated diphenylethers.

Removal of xenobiotic dichlorostearic acid from phospholipids and neutral lipids in cultured human cell lines by B-oxidation and secretion of dichloromyristic acid

Chlorinated fatty acids represent a recently discovered group of potentially hazardous organochlorine pollutants in the environment. The ability of human cells to incorporate and metabolise this type of fatty acids has never been investigated. The aim of the present study was, therefore, to investigate if two human cell lines, INT 407 and SH-SY5Y, incorporate and metabolise extracellular dichlorostearic acid. Cells were incubated with 9,10-dichlorostearic acid for 24 hr, and the amounts of chlorinated fatty acids in cells and culture medium analysed every two days for up to 6 or 10 days. Lipids were separated by solid phase extraction, transesterified to fatty acid methyl esters, and analysed by gas chromatography in combination with a halogen specific detector (GC/XSD). Dichlorostearic acid, dichloropalmitic acid and dichloromyristic acid were found in phospholipids and in neutral lipids of the INT 407 cells. Both cell lines secreted considerable amounts of dichloromyristic acid into the culture medium. Cellular or secreted metabolites shorter than dichloromyristic acid were not found. Taken together, the results suggest that human cells may (1) incorporate chlorinated fatty acids into membrane lipids and storage lipids, (2) metabolise cellular dichlorostearic acid to dichloropalmitic acid and dichloromyristic acid by B-oxidation; but that further metabolism is hindered, possibly because of the chlorine atoms, and (3) remove formed dichloromyristic acid by secretion. The removal of cellular dichloromyristic acid might represent an important cellular defence mechanism and deserves further investigations.

New halogen-specific detector applied to the analysis of chlorinated fatty acids

A new halogen-specific detection method (XSD) was tested for determination of chlorinated fatty acids in marine biota. In XSD, an increased emission of ions and electrons is caused by the high-temperature combustion of halogen-containing compounds. The detection limit of methyl dichlorooctadecanoate and the selectivity at a reactor temperature of 900 degrees C match those of electrolytic conductivity detection (ELCD). The relative standard deviation is less than 11% for > or =0.2 ng methyl dichlorooctadecanoate. An XSD chromatogram of a complex sample, chlorinated fatty acid methyl esters liberated from fish lipids, agreed with a previously obtained ELCD chromatogram.

Inhibitory effect of threo-9,10-dichlorostearic acid on the mutagenic activity of MeIQx, 2-AF and B[a]P in the Ames/Salmonella test

The mutagenic activity of threo-9,10-dichlorostearic acid, one of the chlorinated fatty acids identified in fish lipids, was examined in the Ames/Salmonella test. No mutagenic activity was found on any of the Salmonella typhimurium strains TA 98, TA 100 and TA 102, either with or without S9 activation. On the other hand, dichlorostearic acid showed an inhibitory effect on the mutagenic activity of the indirectly-acting mutagens 2-amino-3, 8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 2-aminofluorene (2-AF) and benzo[a]pyrene (B[a]P) using strain TA 98 in the presence of S9. However, no inhibition was observed when mixing MeIQx and S9 before the addition of dichlorostearic acid. Furthermore, dichlorostearic acid did not show any inhibitory effect on the mutagenic activity of the directly-acting mutagen 4-nitroquinoline-N-oxide (4NQO) using the tester strains TA 98 and TA 100. We, therefore, suggest that dichlorostearic acid interacts with the enzymes of the S9 mix, thereby dose-dependently inhibiting the transformation of MeIQx, 2-AF and B[a]P into their active forms.