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(T/EH054) Effects of persistent organic pollutants (POPs) on reproduction in fish eating birds. de Roode, Daphne1, Bosveld, Albertus1, 1 ABSTRACT- Fish eating birds are at the top of the aquatic food chain, through which they accumulate lipophilic persistent organic chemicals. Their reproduction failures have been described on a global scale, and are thought to arise from either of multiple causes. One of these is embryotoxicity and in this background, attention has been focussed on Ah-receptor agonists such as PCBs, and more recently, endocrine disruptors. In analogy with Baltic predatory fish, where reproductive disorders have been related to contaminant induced thiamine deficiency, this mechanism is also suggested as a possible cause for reproductive disorders in birds. Thiamine is an important cofactor for three enzymes in the central metabolism generating metabolic energy in the form of NAD(P)H. In order to study possible mechanisms that evoke embryotoxicity in birds, egg injection experiments are carried out with both model compounds and extracts from the field. First, an optimised injection procedure has been developed using a more natural carrier obtained from yolk lipids. Tested compounds include the pesticide paraquat (which is thought to induce redox cycling), the antibiotic furazolidone (which is thought to inhibit thiamine phosphorylation into its active form), PCBs 126 and 77, and Aroclor 1248 and 1256 (which are all known to induce EROD activity). Paraquat and furazolidone resulted in effects on thiamine dependent enzyme activities, as well as on histological structures in lymphoid organs and brain which are known for thiamine deficiency. Thus, for these compounds the proposed mechanism of induced thiamine deficiency may play a role. However, PCBs did not seem to interfere with thiamine homeostasis but repeatedly caused high mortality rates during the first few days of incubation. Now, the focus of research is to gain insight into the processes that occur during these specific stages. Parameters under study include biometry, biochemical measurements, and histopathology of lymphoid organs and brain. Key words: embryotoxicity, birds, enzymes, POPs |
