Figure 5: Immunocytochemical detection of iNOS after treatment with Pb for 6 hours. The graph of the arbitrary gray values of the immunocytochemical staining for iNOS after treatment with Pb showed a significant elevation of this protein (*p<0.05) after treatment with Pb. The increased iNOS expression appears to be a ROSdependent process. The gray values of at least 100 HaCaT cells were identified per treatment group (i.e. n=100 cells for the control group (H2O) and n=100 cells for the Pb group). Comparisons of mean gray values of the immunocytochemistry analyses were performed with the use of one-way ANOVA (Magnification=500 fold; Bars=10 μm).