Effects of some chelating agents on the uptake and distribution of ²⁰³Hg²⁺ in the brown trout (Salmo trutta): studies on ethyland isopropylxanthate, diethyl- and diisopropyldithiophosphate, dimethyl- and diethyldithiocarbamate and pyridinethione

Abstract

Brown trout, Salmo trutta, were exposed to water containing 0.1 μg/l ²⁰³Hg²⁺, alone or with potassium ethylxanthate (PEX), sodium isopropylxanthate (SIX), sodium diethyldithiophosphate (SEP), sodium diisopropyldithiophosphate (SIP), sodium dimethyldithiocarbamate (SMC), sodium diethyldithiocarbamate (SEC) or sodium pyridinethione (SPyr), respectively. After 1 week the uptake and distribution of the ²⁰³Hg²⁺ in the fish were examined by gamma spectrometry. SIX, SIP, SMC, SEC and SPyr induced 2–3 times higher ²⁰³Hg²⁺ concentrations in most tissues in comparison with trout exposed to ²⁰³Hg²⁺ only. In the trout exposed to PEX slightly enhanced ²⁰³Hg²⁺ levels were found only in some tissues, and after exposure to SEP a few tissues showed decreased ²⁰³Hg²⁺ concentrations. Determinations of chloroform/water partition coefficients showed that lipophilic chelates are formed between all the examined substances and the ²⁰³Hg²⁺. However, SIX, SIP, SMC, SEC and SPyr, which induced markedly increased tissue levels of the metal, formed ²⁰³Hg²⁺ complexes with higher lipophilicities than SEX and SEP. A facilitated penetration of the lipophilic ²⁰³Hg²⁺ complexes over the gill membranes may underly the increment in the tissue levels of the metal, and the relative lipophilicity of the complexes may be of importance for this effect. In some instances, as with SEP, the ²⁰³Hg²⁺ chelated in complexes with low lipophilicity may even be less able to acumulate in some tissues than the non-complexed metal.