Figure 1. NAC prevents MeHg toxic effects on DNA synthesis and cell survival in embryonic cortical cultures.

A: Concentration-dependent effects of MeHg on [³H]-Thy incorporation in cortical cultures. Cells were exposed for 24 hrs to vehicle or 0.1, 1, 1.5, 2, 3 or 6µM MeHg at zero time. [³H]-Thy was added at 20 hrs and cells were collected at 24 hrs for analysis. MeHg exposure induced a concentration-dependent reduction in DNA synthesis. B: Concentration-dependent effect of NAC on MeHg-induced inhibition of DNA synthesis. Cells were exposed or not to MeHg (3µM) and/or NAC (3 – 1,000µM) for 24 hrs. NAC treatment increased thymidine incorporation at high concentrations (>100µM) and induced a dose-dependent protection against the negative effects of MeHg. C: Protective effect of NAC against MeHg-induced cell death. Cells were exposed or not to MeHg (3µM) and/or NAC (300µM) for 24 hrs and total numbers were assessed under phase microscopy. NAC cotreatment completely abolished MeHg-elicited neuronal death. D: Influence of treatment paradigm on NAC protective effects in vitro. NAC (300µM) exerted protective effects only when it was administered at zero time concurrently with MeHg (3µM). However, when NAC was added to the culture media either 4 or 24 hours before MeHg and removed prior to mercury exposure, no protection was measured. Data are expressed as the mean ± sem of 3 independent experiments for all groups, performed in quadruplicates for every condition. *P<0.05; **P<0.01; ***P<0.001 vs control; #P<0.05; ###P<0.001 vs MeHg.