MICROANALYTICAL STUDY OF THE ALUMINUM DISTRIBUTION IN BULLHEAD (ICTALURUS-NEBULOSUS) GILLS

Different microscopical and microanalytical techniques were used to in vestigate the distribution of aluminum at the gill level of ''acid-res istant'' bullhead fish, exposed to acidified water (pH 4.3) and an ele vated level of aluminum (1 mg A1/L, exposure period = 7 days). In the control group, aluminum could not be detected in or on the gills by la ser microprobe mass spectrometry (LMMS) and scanning transmission elec tron microscopy-energy-dispersive X-rays (STEM-EDX). Electron-dense de posits were located on the lamellae edges as well as inside the gill t issue of fish exposed to acidified aluminum-containing water. The elec tron-dense deposits consisted of small spheres and seemed to accumulat e in delimited cell areas. The deposits were shown to contain elevated levels of aluminum and phosphorus. Aluminum was thus found on the gil l borders, where it is likely associated with the mucus layer, in the apical regions of epithelial cell in chloride cells and macrophages. M icro-PIXE measurements provided quantitative data.