RESULTS AND DISCUSSION
POPULÄRVETENSKAPLIG SAMMANFATTNING
Ett flertal miljögifter har visats kunna störa djurs hormonsystem genom att de liknar det honliga könshormonet östrogen. Därmed kan dessa miljögifter störa viktiga processer i kroppen såsom till exempel reproduktionsbeteendet och utvecklingen av reproduktionsorganen. För att påvisa ett ämnes
östrogenliknande egenskaper har flera olika tester utvecklats. I de flesta av dessa tester utnyttjas odlade celler där man mäter om om kemikalierna påverkar cellerna på samma sätt som östrogen gör. Eftersom dessa tester inte tillfredställande nog kan förutsäga effekterna i ett intakt djur har heldjurstester inom olika djurgrupper efterfrågats.
I avhandlingen föreslår jag fågelägget som ett lämpligt testsystem för östrogenliknande kemikalier. Reproduktionsorganen hos embryon av den japanska vakteln visades vara känsliga för påverkan av östrogenliknande kemikalier. Min slutsats är att äggledar- och testikelmissbildning i
fågelembryoner kan användas som markörer för östrogen aktivitet hos kemikalier. Sådana missbildningar har även observerats hos vilda fåglar. Speciellt äggledarmissbildning är enkelt att studera och borde därför kunna undersökas hos vilda fåglar för att påvisa hormonstörande miljögifter i
naturen. Debatten kring östrogenlika miljögifter har hittills varit fokuserad på effekter på handjuren. Mina forskningsresultat visar att hos fåglar är
honembryot minst lika känsligt som hanembryot för kemikalier med östrogenlik verkan.
Miljögifterna bisfenol A (BPA) och o,p´-DDT orsakade liknande effekter som de syntetiska östrogenerna etynylöstradiol och dietylstilbestrol (DES). Av o,p´-DDT krävdes 100 – 10 000 gånger högre dos än av DES för att ge östrogenliknande effekter på vaktelembryon och av BPA krävdes 1 000 – 100 000 gånger högre dos. Denna studie är den första som visar att BPA har östrogenliknande effekter på fåglar. Flamskyddsmedlet tetrabrombisfenol A gav inte upphov till östrogenliknande effekter i vaktel- eller
kycklingembryoner men orsakade däremot embryodöd vid relativt låga doser.
Exponering av vaktelembryoner för östrogen orsakade bestående förändringar av äggledaren hos den vuxna fågeln, bland annat i
äggskalskörteln. Lokaliseringen av karbanhydras, ett enzym som är centralt i skalbildningsprocessen, påverkades också. Detta fynd, tillsammans med missbildningen i skalkörteln, tyder på en påverkan på äggskalbildningen. Äggskalsförtunning är den mest omfattande störning av reproduktionen som observerats hos vilda fåglar, men den bakomliggande mekanismen är ännu inte klarlagd. Jag föreslår att äggskalsförtunning kan vara uttryck för en skada som grundläggs redan under embryonalstadiet snarare än en effekt som uppträder genom att den vuxna honan utsätts för miljögifter.
ACKNOWLEDGEMENTS
Many people have contributed to this work, in the form of encouragement, support, criticism and input in discussions. I am deeply grateful to everyone, especially:
Björn Brunström, my supervisor, for taking me on as a PhD student, providing me with the opportunity to start the project that I wanted. For giving me (although not without some scepticism) the independence to test some of my ideas. It has been very instructive! Thank you also for being extremely thorough when educating me in scientific writing.
Ingvar Brandt, head of the department and my assistant supervisor. I am truly grateful for all your support and encouragement over the years. Krister Halldin for help with many things, but above all for being fun to work with.
Lena Holm for being such an encouraging collaborator. You and Yvonne Ridderstråle bring about a creative atmosphere which has been very inspiring. Thank you both! Thanks also to Lena for the drawings in the thesis.
Anna-Karin Fridolfsson, for performing sex determination of the embryos. Margareta Mattsson, for providing exellent technical assistance and lots of fun.
Åke Bergman and his team at the Department of Environmental Chemistry, Stockholm University, for synthesizing the labelled compounds.
Former members of the bird group: Magnus Engwall, for helpful
discussions on the project. Katarina Hjelm, Anna Hermansson and Julia Karlsson for good collaboration.
Stefan Gunnarsson, for teaching me about microscope techniques and image analysis programmes, with enormous patience.
Gary Franklin, for improving the language in the thesis.
Everyone at "Ekotox": Marianne, Per, Jan, Emma, Henrik, Lizette, Fariba, Anna, Gunnar, Örjan, Carina, Maria, Misse, Monica, Kifle, Håkan, Rickard and Lillianne, for contributing to this work in one way or another. Your feedback on my seminars and manuscripts has been most valuable to me. I especially want to thank Fariba, for your pep-talks, and Lizette, for always being helpful and for putting up with me as a room mate, especially
considering the significant difference in our sense of order...
Finally, my mother and my brothers, your support has meant a lot to me! My dear friends for sharing good times with me and for seing me through the rough ones. And of course, Frasse, the one and only.
This work was carried out at the Department of Environmental Toxicology, Uppsala University. It was supported by grants from the Swedish
Environmental Protection Agency, the Foundation for Strategic
Environmental Research (MISTRA), the Carl Trygger Foundation, the Swedish Council for Forestry and Agricultural Research (SJFR), Helge Ax:son Johnson Foundation and Hierta Retzius Foundation.
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