Bioaccumulation of cadmiun and its effect on GFAP (+) structures in zebrafish brain.

Water contamination by metal compounds is a worldwide environmental problem. Fish accumulate metals in higher concentrations in their tissues by environmental absorption by the gills and gut. The present report is an attempt to investigate the influence of cadmium exposure on the accumulation of this metal in zebrafish brain and the correlative expression of GAFP marker for the glial cells, the first of the brain parenchyma to encounter metals crossing the blood-brain barrier. Cadmium accumulation in brain was measured by APAT IRSA-CNR method, 3000 Section 3010 division. GAFP immunoreactivity was determined by ABC technique. 18 adult fish were exposed to contaminated water (1.0 mg/L of CdCl2). Groups of 6 fish were killed after 2, 7 and 16 days. Another 18 fish were kept in uncontaminated water as control animals. We reveled that cadmium accumulation increased over time; cadmium concentration in treated fish brain appeared to increase exponentially and it was maximum after 16 days (2 days after: 22.23 ppm ± 1.0; 7 days: 33.16 ppm ± 0.82; 16 days: 45.04 ppm ± 1.02). Immunohistochemical detection of GFAP structures revealed a considerable decrease of the immunoreactive structures during the treatment. In particular, we observed this reduction of GFAP immunoreactivity in the area of the optic tectum, medulla and cerebellum. Our data following treatment with cadmium indicate that a correlation exists between decrement of GFAP expression and cadmium accumulation found in the brain. Maybe cadmium crosses the blood-brain-barrier and it accumulates in the brain, in particular in glial cells.