| dc.description.abstract | Over the last decades, declines have occurred in the range and abundance of several passerines and farmland bird species and even though several possible causes have been suggested, the exposure to environmental contaminants and intensification of agriculture have received much attention. Several environmental contaminants, such as polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and polybrominated flame retardants (PBDEs) have been found to alter steroid hormones levels and may cause adverse effects on reproduction. Present decline in house sparrow numbers appears to be widespread in North-Western Europe since the 1970s. Among a variety of physical and chemical stressors, endocrine disruptive chemicals (EDCs) may contribute to the decline. The aim of the present study was to determine levels of some selected PCBs (PBC-28, -52, -101, -118, -138, -153, -180), PBDEs (BDE-47, -99, -100, -153, -154, -209, hexabromocyclododecane [HCBD]) and OCPs (hexachlorobenzene [HCB], dichloro-diphenyl-dichloroethylene [p,p -DDE]) and to investigate the possible effects of these contaminants on circulating levels of steroid hormones (estrone [E1], 17α-estradiol [αE2], 17β-estradiol [βE2], progesterone [PRO], pregnenolone [PRE], Hydroxylated progesterone [OH-PRO], aldosterone [ALDO], androstenedione [AN], dehydroepiandrosterone [DHEA], dihydrotestosterone [DHT], testosterone [TS]) in adult house sparrows from Leka, Helgeland, Norway. Plasma samples were analysed for steroid hormones by gas chromatography tandem mass spectrometry (GC-MS/MS) and liver samples were analysed for environmental contaminants by gas chromatography-electron capture detection (GC-ECD) and gas chromatography mass spectrometry (GC-MS). It was hypothesized that POPs may have endocrine disrupting effects on the local house sparrow population and can thus interfere with the steroid hormone homeostasis. Multivariate data analysis, principal component analysis (PCA) and orthogonal projections to latent structures (O-PLS), and bivariate correlation test (Spearman s rank correlation test) was applied to evaluate the effects of environmental contaminants and biometrical variables on steroid hormone levels. Multivariate regression analysis indicated no strong relationships between contamination load and steroid hormone levels in adult female and male house sparrows, nor did biometrical variables seem to be very important in explaining the variation of the steroid hormones. However, bivariate correlations revealed negative relationships between PCB-118 and βE2 and p,p -DDE, ∑OCPs and E1 among female house sparrows. Among male sparrows, bivariate correlations indicted positive relationships between DHT levels and PCB-118, BDE-100 and ∑PCBs. Furthermore, it is noteworthy to emphasize that statistical significant models were not found in the multivariate analysis and relationships indicated by bivariate correlations should be interpreted with caution. In addition, these statistical correlations do not represent direct cause-effect relationships and no definite conclusion can be made on possible disruptions on estrogen and androgen levels. | nb_NO |
