Document Detail


Cadmium uptake by cells of renal origin.
MedLine Citation:
PMID:  2254329     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
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.
Authors:
D M Templeton
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  265     ISSN:  0021-9258     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  1990 Dec 
Date Detail:
Created Date:  1991-01-23     Completed Date:  1991-01-23     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  21764-70     Citation Subset:  IM    
Affiliation:
Department of Clinical Biochemistry, University of Toronto, Banting Institute, Canada.
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MeSH Terms
Descriptor/Qualifier:
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:
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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