Trace elements in three marine birds breeding on Reunion Island (Western Indian ocean): part 2-factors influencing their detoxification.

Seabird tissues collected between 2002 and 2004 from Barau's Petrel (Pterodroma baraui), Audubon's Shearwater (Puffinus lherminieri bailloni), and White-Tailed Trop icbird (Phaethon lepturus) colonies on Reunion Island were analyzed for metallothioneins (MTs) and trace element content. The subcellular distribution between soluble and insoluble fractions of Cd, Cu, Fe, Mn, Se, and Zn was determined in liver and kidney. In both, the soluble fraction of the cell concentrated most of the Cd and Se, whereas Fe, Mn, and Zn were preferentially accumulated in the insoluble fraction. The distribution of these elements varied with the tissue, age of the bird, and species. Furthermore, the distributions of Fe and Mn were somewhat influenced by the bird's physical condition. MT levels were measured in the soluble fraction after heat denaturation. The levels of these proteins varied from 5.5 +/- 2.7 mg x g(-1) dry weight (dw) to 11.4 +/- 6.2 mg x g(-1) dw depending on the species and the tissue considered. MT levels were significantly different between liver and kidney only in the White-Tailed Tropicbird. In the three species, MT levels in kidney were significantly higher in adult than juvenile birds. The bird's weight also had an influence on hepatic and renal MT levels, but not the sex nor the reproductive status. The implication of MTs in Cu and Zn homeostasis and Cd and Hg detoxification are discussed. In addition, clues on Hg regulation by Se were found, especially in Barau's Petrel, where the levels of these two elements were significantly correlated.