Antioxidant potential and gap junction-mediated intercellular communication as early biological markers of mercuric chloride toxicity in the MDCK cell line

In this study, the early nephrotoxic potential of mercuric chloride (HgCl2) has been evaluated in vitro, by exposing a renal-derived cell system, the tubular epithelial Madin-Darby canine kidney (MDCK) cell line, to the presence of increasing HgCl2 concentrations (0.1-100 muM) for different periods of time (from 4 to 72 h). As possible biological markers of the tubular-specific toxicity of HgCl2 in exposed-MDCK cultures we analysed: (i) critical biochemical parameters related to oxidative stress conditions and (ii) gap-junctional function (GJIC). HgCl2 cytotoxicity was evaluated by cell-density assay. The biochemical analysis of the pro-oxidant properties of the mercuric ion (Hg2+) was performed by evaluating the effect of the metal salt on the antioxidant status of the MDCK cells. The cell glutathione (GSH) content and the activity of glutathione peroxidase (Gpx) and catalase (Cat), two enzymes engaged in the H2O2 degradation, were quantified. HgCl2 influence on MDCK GJIC was analysed by the microinjection/dye-transfer assay. HgCl2-induced morphological changes in MDCK cells were also taken into account. Our results, proving that subcytotoxic (0.1-10 muM) HgCl2 concentrations affect either the antioxidant defences of MDCK cells or their GJIC, indicate these critical functions as suitable biological targets of early mercury-induced tubular cell injury. (C) 2002 Elsevier Science Ltd. All rights reserved.