Tissue disposition of109cd2+in the brown trout(Salmo trutta)studied by autoradiography and impulse counting†

Abstract

Brown trouts, Salmo trutta, were exposed to ¹⁰⁹Cd²⁺ in concentrations of 0.1, 0.5, 1.0 and 10.0 μg/1 in aquarial water during 1 or 2 weeks. The disposition of the ¹⁰⁹Cd²⁺ in the tissues was then examined by whole‐body autoradiography and gamma spec‐trometry. The tissues accumulating the highest levels of ¹⁰⁹Cd²⁺ were the olfactory apparatus, the gills and the trunk kidney. The autoradiography showed that in the olfactory apparatus there was a labelling of the epithelium of the olfactory rosette, the olfactory nerve and the anterior part of the olfactory bulb of the brain. The cadmium is probably taken up in the nerve cells in the olfactory epithelium and transported via axonal transport to the axonal terminations in the olfactory bulb of the brain. The ¹⁰⁹Cd²⁺ in the gills comprised from about 75% to about 40% of the total body burden of the metal, the highest proportions being present at the lowest cadmium concentrations in the water and at the 1 week exposure interval. The ¹⁰⁹Cd²⁺ in the kidney, which was strongly localized to distrinct areas in the trunk kidney, was present in much higher concentrations after 2 weeks exposure than after 1 week exposure. The liver accumulated a considerable concentration of ¹⁰⁹Cd²⁺. The lowest ¹⁰⁹Cd²⁺ levels were registered in the muscles. The average whole‐fish accumulation of the ¹⁰⁹Cd²⁺ by the fishes was about 50–100 times at the 0.1, 0.5 and l.0 μg/1 concentrations of the metal in the water, whereas at 10 μg/l of ¹⁰⁹Cd²⁺ the average bioaccumulation had diminished to about 10–20 times. The saturation of the uptake in the tissues at the 10 μg/l concentration of the ¹⁰⁹Cd²⁺ was more marked in the gills than in the other tissues. Our results show that some tissues of the brown trout are able to strongly concentrate cadmium from low water concentrations. The accumulation in the olfactory apparatus suggests that cadmium may be injurious for the olfactory sense.