Effects of cadmium and copper on zinc transport kinetics by isolated renal proximal cells |
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Authors: | Bertrand Gachot Philippe Poujeol |
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Institution: | (1) Service de Biologie Cellulaire, Départment de Biologie Cellulaire et Moléculaire, CEN Saclay, 91191 Gif sur Yvette Cedex, France |
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Abstract: | Zinc, cadmium, and copper are known to interact in many transport processes, but the mechanism of inhibition is widely debated,
being either competitive or noncompetitive according to the experimental model employed. We investigated the mechanisms of
inhibition of zinc transport by cadmium and copper using renal proximal cells isolated from rabbit kidney. Initial rates of65Zn uptake were assessed after 0.5 min of incubation. The kinetics parameters of zinc uptake obtained at 20°C were a Jmax of 208.0±8.4 pmol· min−1·(mg protein)−1, aK
m of 15.0±1.5 μM and an unsaturable constant of 0.259±0.104 (n=8). Cadmium at 15 μM competitively inhibited zinc uptake. In the presence of 50 μM cadmium, or copper at both 15 and 50 μM, there was evidence of noncompetitive inhibition. These data suggest that zinc and cadmium enter renal proximal cells via
a common, saturable, carrier-mediated process. The mechanisms of the noncompetitive inhibition observed at higher concentrations
of cadmium or with copper require further investigation, but may involve a toxic effect on the cytoskeleton. |
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Keywords: | Zinc uptake cadmium copper renal proximal cells rabbit kidney |
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