Fig. 4. Propofol increases nitric oxide (NO) production and NO synthase (NOS) activity in Human umbilical vein endothelial cells (HUVECs). ( A ) Time course of propofol-induced NO production in HUVECs. Cells were in control condition, treated with propofol (30 μm) for 10, 30, 60, or 120 min. ( B ) Cells from either control or treated with cyclic strain in the absence or presence of propofol (1–30 μm) for 60 min. ( C ) Cells were treated with propofol (1–30 μm) for 60 min. NOS activities were measured by citrulline formation from cell lysate incubated with (black bars) or without Ca2+(white bars). NOS activity in the absence of Ca2+indicates inducible NOS activity, whereas its activity in the presence of Ca2+represents constitutive NOS activity. Results are shown as mean ± SEM (n = 6). * P < 0.05 versus control. # P < 0.05 versus strain-alone treated cells (analysis of variance [ANOVA]).