SARGAZI M.; ROBERTS N.B.; SHENKIN A.: Cytotoxic studies of Fe and Zn compared with Hg on a monolayer of renal proximal tubular cells (PTC) and the evaluation of cytoprotectants

The toxicity effects of iron (III), zinc and Hg were evaluated between 0, 25, 50, 75, 100 mmol/l final concentrations on PTC in a monolayer culture. Assessment of cell viability used MTT (Thiazol blue) uptake as an indicator of mitochondrial membrane integrity, release of NAG (N-Acetyl-b-D-glucosaminidase) as an indicator of lysosomal damage, LDH (lactate dehydrogenase) as an indicator of plasma membrane integrity and DAPI staining for DNA fragmentation. Studies showed that Fe and Zn reduced cell viability maximally by 40 % and 30 % after 72 and 48 hrs incubation, whereas reduction for Hg was 95 % after 72 hrs at the concentration of 100 mmol/l respectively. Fe and Zn showed an increase (3.7 % and 11 %) in NAG activity, whereas Hg showed an inhibitory effect. All elements induced LDH release 2-3 fold. DNA fragmentation by DAPI staining showed no difference from control for Fe, but there was obvious nuclei condensation for Zn and Hg expressing a typical apoptosis model of cell death. Electron microscopy in treated cells with Fe showed no changes. However in Hg treated cells there was loss of brush borders, the presence of vaccuolated cytoplasm, disruption of mitochondria and loss of nucleus density. Glutathione and Tiopronin showed a significant protective effect on the PTC exposed to Fe, Zn and Hg. However vitamin C and cysteine had no effect on cells treated with Hg. Conclusion: Iron, zinc and mercury showed toxic effect on kidney proximal tubular cells, which include damage to plasma membrane, cytoplasm and/or the nucleus.