Arsenite and UVA cooperate in HO-1 upregulation. HaCaT cells were incubated with 3 μM arsenite (As), 10kJ/m2 UVA (UVA) or left untreated (NT). Dually treated samples were pre-incubated with 3 μM arsenite (As) for 24 hrs and then exposed to UVA. Total protein was collected 4 hrs post exposure and 60 μg resolved via a 12% SDS-PAGE gel. HO-1 was analyzed using anti-HO-1 antibodies and detected by ECL. Equal protein loading was confirmed by reprobing the original membrane with β-Tubulin (A). Blots shown are representative of at least 3 independent experiments. Densitometric analysis of immunoblotting was performed (B). Each bar is the mean of at least 3 independent experiments and the error bars indicate ± S.D. * = significantly different from untreated controls (NT), p<0.05; # = significantly different from singly treated samples, p<0.05.