METAL X-RAY-MICROANALYSIS IN THE OLFACTORY SYSTEM OF RAINBOW-TROUT EXPOSED TO LOW-LEVEL OF COPPER

It has recently been shown that a chronic copper exposure induces spec ific degeneration of olfactory receptor cells in rainbow trout; howeve r, the exact mechanism of action of the metal is not yet known. Using X-ray microanalysis in transmission electron microscopy, we have studi ed the distribution of metal in the olfactory system of fish exposed f or 15, 30 and 60 days to 20 mu g/l of copper. This was done in order t o determine if it was accumulated in receptor cells and transported in to the central nervous system via the olfactory nerve. No copper accum ulation was detected either in the olfactory epithelium, in the olfact ory nerve or in the olfactory bulb. The heavy metal was exclusively fo und within melanosomes of melanophores located in the lamina propria. After 60 days of exposure, the copper content in melanosomes was about two-fold higher than that in controls. As far as some morphological r ecovery took place in the olfactory organ during the metal exposure, w hich lets us suppose that some detoxication mechanism occurs, it could be suggested that melanophores might be somehow involved in such a me chanism.