Elsevier

Biochemical Pharmacology

Volume 53, Issue 12, 15 June 1997, Pages 1889-1900
Biochemical Pharmacology

Research paper
Binding of mercury in renal brus-border and basolateral membrane-vesicles: Implication of a cysteine conjugate of mercury involved in the luminal uptake of inorganic mercury in the kidney

https://doi.org/10.1016/S0006-2952(97)00138-XGet rights and content

Abstract

The influence of the thiols l-cysteine (CYS), glutathione (GSH), and 2,3-dimercapto-1-propanesulfonate (DMPS) on the binding and transport of inorganic mercury (Hg2+) in luminal (brush-border) and basolateral membrane-vesicles isolated from the kidneys of rats was studied using radiolabeled mercury (203HgCl2). Membrane-vesicles were exposed to 1, 10, or 100 μM Hg2+ in the presence or absence of a 3:1 or 10:1 mole-ratio of CYS, GSH, or DMPS relative to Hg2+. Equilibration of mercury with the membrane-vesicles occurred very rapidly, essentially being complete within 5 sec. By 60 sec, binding accounted for 87–97% of intravesicular Hg2+ in the absence of exogenous thiols. All three thiols significantly reduced the fraction of binding, with DMPS being the most effective agent. CYS enhanced the association of Hg2+ with luminal membrane-vesicles relative to that when Hg2+ was added alone, suggesting that conjugation of Hg2+ with CYS promotes the transport of low concentrations of Hg2+. In contrast, an excess of either GSH or DMPS relative to Hg2+ interfered significantly with both the binding and transport of Hg2+ into either luminal or basolateral membrane-vesicles. In summary, the present study is the first to describe the association of Hg2+ with renal luminal and basolateral membrane-vesicles. Evidence was obtained for the involvement of a Hg2+-CYS conjugate as a mechanism by which Hg2+ uptake and binding to luminal membranes occur and for an inhibitory effect of GSH and the chelator DMPS with regard to Hg2+ uptake and binding, demonstrating that extracellular thiols can modulate significantly the renal accumulation of Hg2+.

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    This research was supported by National Institute of Environmental Health Sciences Grant 5 R01-ES05157 and -ES05980. L.H.L. is the recipient of a Research Career Development Award from the National Institute of Diabetes and Digestive and Kidney Diseases (Grant K04-DK02090).

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