Figure 2.
IL-13 increases gas phase NO and total nitrate content in culture medium. (A) Different concentrations of IL-13 (0, 1, 10 ng/ml) were introduced in the culture medium of NHBEs at time t = 0. Gas phase NO release was followed over a period of 48 h by determining steady-state NO concentrations at different times and calculating a flux as described in Materials and Methods. Basal (0 ng/ml) NO flux was small and relatively constant. IL-13 caused a dose-dependent increase in NO flux by up to 2 orders of magnitude (n = 4 or 12; #,&: P < 0.05 compared with 0 and 1 ng/ml, respectively). Results for donor 3 cells; other donors showed similar trends with smaller magnitudes. (B) Total nitrate content in the culture medium shows a dose-dependent increase after the cells were exposed to IL-13 for 48 h (n = 13 or 14) (#,&: P < 10−5 compared with 0 and 1 ng/ml, respectively).