Electrical and freeze-fracture analysis of the effects of ionic cadmium on cell membranes of human proximal tubule cells.
We previously reported that cell cultures of human proximal tubule (HPT) cells respond to ionic cadmium in a manner consistent with well-defined Cd(2+)-elicited responses reported for in vivo systems. However, one unique finding was that the transepithelial electrical resistance and tight junction sealing strands were altered as a result of Cd2+ exposure at micromolar concentrations. These alterations are reexamined in detail in the present report to determine whether the Cd(2+)-induced alterations are specific alterations in the tight junction structure or reflect a general alteration in the cell membrane. Exhaustive analysis of tight junction sealing strands demonstrated no significant alterations due to Cd2+ exposure, even at the concentration that elicited a significant reduction in transepithelial resistance. Further analysis of intramembrane particle distribution demonstrated a significant increase in apical intramembrane particles, indicating that Cd2+ exposure altered the characteristics of the apical cell membrane. Overall, the results were consistent with evidence of Cd(2+)-induced alteration in the apical cell membrane of the HPT cell.
Hazen-Martin
D J
DJ
Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston 29425.
Todd
J H
JH
Sens
M A
MA
Khan
W
W
Bylander
J E
JE
Smyth
B J
BJ
Sens
D A
DA
D002104:Cadmium / Q000494:pharmacology*; D002413:Cations, Divalent / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D017097:Electric Impedance; D005614:Freeze Fracturing; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D002413:Cations, Divalent; D002104:Cadmium; D000242:Cyclic AMP; D000254:Sodium-Potassium-Exchanging ATPase