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Mercury is Transported by the Retinal Pigment Epithelium as an S ‐conjugate of Cysteine
Author(s) -
Zalups Rudolfs K,
Battle Jamie R,
Bridges Christy C
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a1137-a
Subject(s) - mercury (programming language) , cysteine , chemistry , conjugate , retinal pigment epithelium , biophysics , retina , biochemistry , retinal , apical membrane , epithelium , transporter , efflux , microbiology and biotechnology , biology , membrane , enzyme , genetics , mathematical analysis , mathematics , neuroscience , computer science , gene , programming language
Inorganic mercury is an important environmental contaminant that has deleterious effects on numerous organ systems, including the eye. Following exposure to inorganic mercury, the rod photoreceptor cells are damaged, and scotopic vision is compromised. The retinal pigment epithelium (RPE) is located strategically between the outer segments of the photoreceptor cells and the choroidal blood supply. One of its primary functions is to provide nutritive support to the outer retina. In doing so, the RPE may also present the photoreceptor cells with toxicants that are present in blood. Recently, it has become clear that mercuric ions gain access to the epithelial cells via a mechanism of molecular mimicry, whereby a thiol S‐conjugate of mercury, especially the cysteine (Cys) S ‐conjugate (Cys‐ S ‐Hg‐ S ‐Cys), acts as a mimic of an amino acid at the site of an amino acid transporter. The purpose of the current study was to analyze the transport of Cys‐ S ‐Hg‐ S ‐Cys across the apical plasma membrane of RPE cells. The transport of Cys‐ S ‐Hg‐ S ‐Cys was characterized in cultured human ARPE‐19 cells grown in 24‐well plates. Analyses of time‐course, temperature‐dependence, saturation‐kinetics, and substrate‐specificity indicate that Cys‐ S ‐Hg‐ S ‐Cys is a transportable substrate of one or more sodium‐dependent transporters located on the apical surface of the ARPE‐19 epithelial cells. The results of this study provide important insight into the mechanism of mercury toxicity in the retina.