FIG. 8.

Arsenite induces c-fos and c-jun expression and enhances DNA synthesis. (A) Northern blot analysis of RNA extracted from arsenite-stimulated PC12 cells in the presence or absence of tyrphostin AG1478. PC12 cells were treated (Arsenite) or untreated (Control) with 400 μM arsenite for 30 min in the presence (Arsenite + AG1478) or absence of tyrphostin AG1478. The cells were harvested and analyzed for expression of c-fos mRNA, c-jun mRNA, and 18S rRNA by Northern blot analysis. The signals were quantitated with a PhosphorImager, and following normalization to 18S rRNA, relative fold mRNA induction for c-fos and c-jun mRNA expression was determined (bottom panel). (B) Arsenite increases cell population in S phase. PC12 cells were starved in serum-free medium for 48 h. Starved cells were either treated with 400 μM arsenite for 24 h or continual kept in serum-free medium for another 24 h. For cell cycle distribution analysis (as described in Materials and Methods), the cells were collected before arsenite treatment [Serum free (48 h)], after arsenite treatment [Serum free (48 h) + Ars (24 h)], or without treatment [serum free (72 h)]. The percentages of the cells in various cell cycle phases are indicated as means ± standard deviations. Results were from three different experiments.