PARENT SESSION

(07-01) Activities of anti-xenobiotic defense mechanisms determine sensitivity to pollutants and environmental selection of aquatic organisms.

Bresler, Vladimir^*,1, Fishelson, Lev², Mokady, Ofer¹, Abelson, Avigdor¹, ¹ Institute for nature conservation research, Tel-Aviv University, Tel-Aviv, Israel² Department of Zoology, Tel-Aviv University, Tel-Aviv, Israel

ABSTRACT- Only few scientists know that all organisms must protect themselves against xenobiotics. We examined the activities of various anti-xenobiotic defense mechanisms in different aquatic and terrestrial species from protozoa to vertebrates. We showed that membrane export pumps (system of active transport of organic anions [SATOA], which eliminate various hydrophilic anionic xenobiotics and by-products, and multixenobiotic- resistance-mediated transporter [MXRtr], which eliminate hydrophobic and amphiphilic xenobiotics) formed the most important biologically first line of the defense. These pumps were already detected in protozoa and in metazoan they are functionally expressed in external epithelia, specialized excretory organs and histohematic barriers. The pumps activities were species- and tissue-specific. Their mean activities were significantly higher in specimens collected from the polluted sites then from the clean sites. The frequency polygon of pumps activities in animals from the polluted sites exhibited a marked shift to higher values as compared to those from the clean site. Decreased KM and increased Vmax determine the enhanced activity in the polluted sites. We detected strong negative correlation between activities of export pumps and levels of clastogenicity, genotoxicity and environmental pathology. Laboratory studies and field experiments with transplantation of the animals from site to site demonstrated higher resistance of specimens from the polluted sites to acute toxic actions. Our data testify that the activities of export pumps play an impotent role in surviving in chronically polluted environment and may be an important factor for environmental selection. The formation of multixenobiotic-resistant biota, especially bacteria, protozoa, worms and insects, may be more dangerous for humans than direct action of pollutants and decreased biodiversity.

Key words: export pumps, selection, population dynamics