Endogenous nitric oxide counteracts antigen-induced bronchoconstriction.

In anesthetized, artificially ventilated guinea pigs immunized against ovalbumin, challenge with aerosolized ovalbumin (0.1 mg) elicited a substantial and sustained increase of insufflation pressure. The inhibitor of endogenous nitric oxide (NO) synthesis, L-NAME (N omega-nitro-L-arginine methylester, 30 mg kg-1 i.v.), markedly augmented the response, the potentiation of which could be prevented by NO (20 p.p.m.) in the inhaled air. The results indicate an inhibitory effect of endogenous NO on antigen-induced bronchoconstriction.