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 (HP T) cells respond to ionic cadmium in a manner consistent with well-def ined Cd2+-elicited responses reported for in vivo systems. However, on e unique finding was that the transepithelial electrical resistance an d tight junction sealing strands were altered as a result of Cd2+ expo sure at micromolar concentrations. These alterations are reexamined in detail in the present report to determine whether the Cd2+-induced al terations 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 alterat ions due to Cd2+ exposure, even at the concentration that elicited a s ignificant reduction in transepithelial resistance. Further analysis o f intramembrane particle distribution demonstrated a significant incre ase in apical intramembrane particles, indicating that Cd2+ exposure a ltered the characteristics of the apical cell membrane. Overall, the r esults were consistent with evidence of Cd2+-induced alteration in the apical cell membrane of the HPT cell.