NITRIC-OXIDE SYNTHASE INHIBITION IS DETRIMENTAL TO CARDIAC-FUNCTION AND PROMOTES BRONCHOSPASM IN ANAPHYLAXIS IN RABBITS

We studied the effects of a nitric oxide synthase (NOS) inhibitor, N-o mega-nitro-L-arginine-methyl ester (L-NAME), on cardiac depression and bronchospasm provoked by systemic anaphylaxis in vivo in rabbits. Ani mals pretreated with L-NAME showed lower survival rates than control a nimals pretreated with normal saline. The survival rate in L-NAME-pret reated animals was increased by the administration of L-arginine after initiation of anaphylaxis. Cardiac output fell significantly in anima ls pretreated with L-NAME compared with controls, although venous retu rn was increased. In animals pretreated with L-NAME, pulmonary resista nce was significantly increased, and administration of arginine attenu ated the bronchospasm. In conclusion, these results, along with the lo w survival rates in the L-NAME-treated animals, suggest that NO produc tion may be beneficial to cardiac depression and bronchospasm in anaph ylaxis in vivo.