The uptake of essential (Zn) and nonessential (Pb) metals in three major parts (liver, gills and muscle) of African catfish (Clarias gariepinus) exposed singly and to the mixture of the metals at environmentally relevant concentrations (2.0 mg/L) for 96 h was investigated. Marked differences were observed both in the effectiveness of the parts to bioaccumulate and in the membrane passages of each metal. Like several studies, concentrations of both Zn and Pb were noticeably higher in the liver and gills than in the muscle tissue. Pb uptake rates were consistently increasing in the presence of Zn in all the parts. However, the Zn concentrations that accumulated in the presence of Pb significantly decreased, which is suggestive of the antagonistic nature of Pb towards Zn in the solution. The results demonstrate the complexity of the uptake processes occurring in media containing a mixture of metals at environmentally relevant concentrations. These interactions may be of key significance in understanding and predicting metal uptake, accumulation, and toxicity in multimetal exposure scenarios.
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