Subchronic Toxicity of Baltic Herring Oil and its Fractions in the Rat I: Fractionation and Levels of Organohalogen Pollutants

Abstract

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.

Gonadotoxic effect of polychlorobiphenyls

“…Fatty tissue ranks first by the level of toxicants in this series. Published data also indicate higher accumulation of PCB in the fat [10], which is determined by high lipophilia of these compounds.…”

Subchronic Toxicity of Baltic Herring Oil and its Fractions in the Rat (III) Bone Tissue Composition and Dimension, and Ratio of n‐6/n‐3 Fatty Acids in Serum Phospholipids

“…Cold pressed Nordic Sea Capelin oil was included in the study in order to provide a nutritionally equivalent control group. Herring catch, fractionation procedure, the methods and results of chemical analysis of fish oils and fractions are described in detail elsewhere (Öberg et al 2002). In brief, fish oils and fractions were analysed for eight chlorinated biphenyls, all 2,3,7,8‐substituted CDD/Fs, 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.…”

“…The fat concentration in the R34 diet is standardised to 3.5 % (mainly fish fat). 2 The daily consumption of CDD/F‐TEQ, calculated according to WHO‐TEF (Van den Berg et al 1998), was estimated from the contaminant concentrations in herring oil and its fractions (Öberg et al 2002), the fish fat content of the diets and the estimated daily food consumption (Stern et al 2002). …”

“…Due to the concern of health effects of various organohalogen pollutants, including dioxins and PCBs in fatty fish, a subchronic toxicity study was carried out in the rat (Stern et al 2002; Öberg et al 2002). Rats were given Baltic herring oil or its fractions at different doses in the diet to examine the contribution of different organohalogen pollutants to toxicity and biological effects.…”

“…Rats were given Baltic herring oil or its fractions at different doses in the diet to examine the contribution of different organohalogen pollutants to toxicity and biological effects. We reported that CYP1A1 induction and hepatic Vitamin A depletion could be related to pollutants such as PCDD/Fs and PCBs, despite the fact that these compounds contribute on a weight basis to a minor part of the extractable organically bound chlorine (Öberg et al 2002). We have also reported changes in total bone mineral density (determined by the bone‐ash method) in rats exposed to Baltic Herring oil or its fractions (Stern et al 2002).…”