Effects of environmental and natural estrogens on vitellogenin production in hepatocytes of the brown frog (Rana temporaria).

The objective of this study was to investigate the ability of the natural estrogens and synthetic estrogens as well as the estrogen mimics to induce estrogen-receptor mediated vitellogenesis in primary hepatocytes of the brown frog (Rana temporaria). Based on EC50 values the following order was determined for the potency of the estrogens: 17beta-estradiol (EC50: 19-43 nM) approximately ethynylestradiol (EC50: 13-80 nM)>estrone (EC50: 218-241 nM)>DES (EC50: 338-3537 nM). Exposure to bisphenol A and methoxychlor concentrations up to 100 microM did not have any effect on in vitro vitellogenesis.

Ecotoxicological suitability of floodplain habitats in The Netherlands for the little owl (Athene noctua vidalli).

This study describes the actual risks of exposure to contaminants, which little owls (Athene noctua vidalli) face in Dutch river floodplains. The results indicate that PCBs pose a risk: not only are levels in little owls from floodplains higher than levels found in little owls from a reference site but the PCB patterns in owls from the floodplains also indicate induction of hepatic cytochrome P450 enzymes by dioxin like compounds, possibly PCBs. Of the heavy metals, only cadmium is thought to pose a risk in certain conditions, for example, when little owls are feeding only on earthworms over a prolonged period of time. The results do not indicate any effects on the occurrence of prey items of the little owl like for instance earthworm, beetles and shrews. Hence, it is not expected that little owls will be affected by diminishing prey availability due to contamination.

Lack of a distinct gradient in biomarker responses in small mammals collected at different distances from a highway.

This study describes biomarker effects in small mammals exposed to traffic emissions. Animals were collected at 10-50 m (site 1), 150-200 m (site 2), and 5 km (site 3) from a very busy highway (A2). To distinguish between routes of exposure, strictly carnivorous common shrews ( Sorex araneus) and predominantly herbivorous bank voles ( Clethrionomys glareolus) were collected. As a measure of exposure to polycyclic aromatic hydrocarbons (PAHs), aromatic DNA adduct levels were determined by (32)P-postlabeling techniques in tissue from heart, lung, and liver. Lead (Pb), cadmium (Cd), and copper (Cu) levels were analyzed in kidney as a measure of exposure to heavy metals. EROD and PROD activity and retinoid levels were determined in liver as effect biomarkers for exposure to PAHs and polyhalogenated aromatic hydrocarbons (PHAHs). Relatively high Cd levels in S. araneus and in particular elevated DNA adduct levels in C. glareolus indicated that small mammals at site 3 were exposed to more compounds than at sites 1 and 2 (3 > or = 1 > 2). The latter effect is probably due to an incidental and actual input of airborne pollutants that is deposited on plant surfaces. By consumption of above-ground vegetation, voles are chronically exposed to this pollution. Relatively high background input of PAHs probably hinders that the traffic-related gradient of airborne PAH concentrations found in an earlier study is reflected in DNA adduct levels in small mammals in the present study. Moreover, historical biomarkers for exposure to traffic emissions, such as increased kidney Pb levels, increased hepatic EROD activity, and disturbed hepatic vitamin A homeostasis are no longer applicable to indicate differences in exposure. This is a result of the ban on addition of Pb and chlorinated scavengers to gasoline and of cleaner combustion techniques, which were enforced by law over the past decade. Finally, it is advisable to use only juvenile small mammals for in situ monitoring of diffuse pollution because DNA adduct levels increased with age.