Figure 1.

Caspase 3 activity (left) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT; right) were determined in pulmonary artery endothelial cells (PAECs) incubated in normoxia and treated with vehicle or lipopolysaccharide (LPS) for 48 hours to determine the time and concentration of maximum response. The number of experiments appears in the bars. The vehicle for LPS was physiological saline. Caspase 3 activity was increased and MTT incorporation was decreased by exposure for 48 hours to 0.5 μg/mL LPS (t tests), consistent with apoptosis and necrosis injury of these cells. LPS-induced increments in these end points were lower in cells treated for greater or lesser time periods or with differing concentrations of LPS.