Cell cycle analysis of HPASMC exposed to hypoxia and BPS. Cultured HPASMC were exposed to 21% and 2% oxygen with or without 10 μM BPS for 24 hours. Cells were harvested and DNA fragmentation was analyzed using flow cytometry and propidium iodide staining. Area definitions on DNA histograms: C, G0/1 phase; D, S phase; E, G2/M phase. Moderate hypoxia (2% oxygen) increased, whereas BPS significantly decreased ratios of S plus G2/M and G2/M phases. Histograms are representative and bar graph shows data expressed as means ± SE (n = 4). Open bars, ratios of G2/M phases; solid bars, ratios of S plus G2/M phases. *P < 0.05 versus 21% oxygen control; †P < 0.05 versus 2% oxygen without BPS.