Fig 2.

Inhibiting iNOS activity abrogates the stressor-induced increase in microbicidal activity. (A) Peroxynitrite production was significantly higher in PMA/LPS/IFN-γ-stimulated splenic macrophages derived from mice exposed to the SDR stressor (*, P < 0.05 versus all other groups at designated time points). However, the addition of L-NMMA to the cultures prevented the stressor-induced increase in peroxynitrite production. Values are fluorescence intensity means ± the SE (n = 6 HCC and n = 7 SDR from two different experiments). (B) Exposure to the SDR stressor significantly increased the number of bacteria killed at the 90 min time point (*, P < 0.05 versus HCC control). However, the addition of the iNOS inhibitor L-NMMA prevented this stressor-induced increase in bacterial killing (n = 6 HCC and n = 6 SDR from two different experiments). Overall, the bacterial levels were lower in the cultures containing cells from SDR-exposed mice (main effect: *, P < 0.05). (C) Cells from SDR-exposed mice killed a significantly greater percentage of the E. coli than did cells from the nonstressed HCC control mice (*, P < 0.05). Addition of L-NMMA prevented the stressor-induced increase in the number of bacteria killed (n = 6 HCC and n = 6 SDR from two different experiments).