LACK OF INHIBITORY EFFECT OF DEXAMETHASONE ON EXHALATION OF NITRIC-OXIDE BY HEALTHY HUMANS

Nitric oxide (NO) is present in the breath exhaled from healthy humans , The location and subtype of the NO synthase responsible for the expi red NO are unknown, As dexamethasone inhibits the induction of NO synt hase, we evaluated the effect of administering dexamethasone (4 mg/day for 2 days) on the amount of NO exhaled by eight healthy men. The amo unt of NO showed a significant linear correlation with the duration of exhalation, allowing the rate of NO release to be calculated, The rat e of NO release was 0.047+/-0.023 nmol/s before drug administration, T here was no significant change in the release rate at the end of the 2 -day administration of drug or at 5 days after cessation, Serum concen trations of interferon-gamma and interleukin-1 beta were unaffected by the administration of dexamethasone, These results suggest that the N O released from the human airway under normal conditions is not genera ted by the action of inducible NO synthase.