| Cadmium uptake by cells of renal origin. | |
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MedLine Citation:
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PMID: 2254329 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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We compared the ability of rat glomerular mesangial cells and LLC-PK1 cells to take up Cd2+ from solution. The former are smooth muscle-like cells of mesenchymal origin, the latter an established line of proximal tubular epithelium. Both cells, as well as primary glomerular epithelia, accumulated Cd2+ against a concentration gradient in a time-dependent manner. Uptake by mesangial cells obeyed a Michaelis model with an apparent Km of 19 microM and could be described by an initial rapid step of surface binding followed by rate-limiting internalization. In contrast, uptake by LLC-PK1 cells was non-saturable under accessible concentrations of Cd2+ and internalization was not a necessary consequence of association with the cell surface. In several other cell types, Cd2+ uptake has been shown to be inhibited by blockage of cell-surface sulfhydryl groups. In contrast, uptake by neither mesangial nor LLC-PK1 cells was depressed by N-ethylmaleimide, which actually enhanced the surface binding and to a lesser extent the uptake by the LLC-PK1 cell line. Neither depended on metabolic energy for uptake or utilized Ca2+ channels. The internalization process was temperature dependent and was obliterated at 2 degrees C. In mesangial cells, this allowed direct observation of the internalization event from a presaturated surface pool. The rate of this process was consistent with the Vmax calculated from the Michaelis model. Surface binding and uptake were decreased by binding of Cd2+ to serum proteins and albumin and were much less dependent on the presence of low molecular weight components of serum. Therefore, these cells may be especially sensitive to Cd2+ at concentrations encountered in vivo because of the low protein content of the plasma ultrafiltrate. Surface binding of Cd2+ to mesangial cells was suppressed by competing divalent ions following the order of the Irving-Williams series (Mn less than Co less than Ni less than Cu greater than Zn), although Zn2+ showed the greatest effect on internalization. In LLC-PK1 cells, Zn2+ and Cu2+ were both effective in decreasing Cd2+ uptake. We conclude that Cd2+ uptake by the tubular epithelial cells is rapid and independent of specific cell surface interactions, whereas uptake by rat mesangial cells follows binding to a specific surface ligand saturating at about 1.5 x 10(7) copies/cell. In both types of cells the uptake appears quite specific for Cd2+ and shows some cross-reactivity with other metal cations explicable by competitive ligand binding. |
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Authors:
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D M Templeton |
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Publication Detail:
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Type: In Vitro; Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: The Journal of biological chemistry Volume: 265 ISSN: 0021-9258 ISO Abbreviation: J. Biol. Chem. Publication Date: 1990 Dec |
Date Detail:
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Created Date: 1991-01-23 Completed Date: 1991-01-23 Revised Date: 2006-11-15 |
Medline Journal Info:
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Nlm Unique ID: 2985121R Medline TA: J Biol Chem Country: UNITED STATES |
Other Details:
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Languages: eng Pagination: 21764-70 Citation Subset: IM |
Affiliation:
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Department of Clinical Biochemistry, University of Toronto, Banting Institute, Canada. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Animals Biological Transport / drug effects Cadmium / metabolism* Calcium / pharmacology Cell Adhesion / drug effects Epithelium / metabolism Ethylmaleimide / pharmacology Glomerular Mesangium / metabolism Kidney / cytology, metabolism* Male Rats Rats, Inbred Strains Serum Albumin / metabolism Sulfhydryl Compounds / metabolism Time Factors |
| Chemical | |
Reg. No./Substance:
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0/Serum Albumin; 0/Sulfhydryl Compounds; 128-53-0/Ethylmaleimide; 7440-43-9/Cadmium; 7440-70-2/Calcium |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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