Figure 3. Cell viability and cytoskeleton organization.

(a) MTT assay results: Penicillin G alone does not affect podocyte viability at any used concentration from 50 to 700 IU/ml (group bars on the left). PA-induced loss of viability (black bars) is not influenced by pre-incubation with 50 IU/ml penicillin (light rose bars), whereas it is dose-dependently prevented by 100, 500 and 700 IU/ml Penicillin G (dark violet, light violet and gray bars). Best effects of Penicillin are observed at lower doses of PA (2.5 ug/ml, group bars on the left). Graph bars indicate mean ± SD values from three independent experiments. **  =  P<0.001 vs. PA alone, ^#  =  P<0.05 vs PA alone. (b) Double staining for vinculin and actin. In control condition, vinculin is periodically expressed at the cell periphery, at the tip of actin stress fibers, as shown by co-localization with actin (left panels). These features are modified after incubation with either 2.5 and 10 ug/ml PA; vinculin is irregularly dispersed in the cell body, actin stress fibers are progressively reduced by 2.5 and 10 ug/ml PA, and co-localization of the two molecules occurs in the cell body and is absent at the cell periphery (middle panels). Preincubation with Penicillin G (500 Units/ml) partially (PA 10 ug/ml) or completely (PA 2.5 ug/ml) preserves the cytoskeletal structure from PA damage (right panels); the antibiotic prevents loss of actin fibers even with PA dosages of 10 ug/ml. With 2.5 ug/ml PA, vinculin-positive focal adhesions are also maintained at their location. Scale bars  =  20 um.