BETA-ADRENERGIC AGONIST-INDUCED NITRITE PRODUCTION IN ISOLATED PIG CILIARY PROCESSES

Background: We performed an experiment to assess whether in ciliary pr ocesses adrenergic-receptor agents can modulate the production of nitr ite, an oxidized metabolite of nitric oxide (NO). Methods: The porcine ciliary processes and the iris were dissected and stored at -20 degre es C. Later, tissues were thawed, and nitrite measured by Griess react ion, before and 2 h after exposure to various drugs. Results: In the c iliary processes, but not in the iris, the alpha-, beta-adrenergic rec eptor agonist, norepinephrine (0.01-10 mu M), increased nitrite produc tion (95 +/- 12%, P <0.01). The norepinephrine-induced (0.1 mu M) nitr ite production was inhibited by the inhibitor of NO synthase, N omega- nitro-L-arginine methyl ester (0.5 mM; P <0.05) and by the non-selecti ve beta-adrenergic receptor antagonist, propranolol (10 mu M; P <0.01) , but not by the non-selective alpha-adrenergic receptor antagonist, p hentolamine (10 mu M). Conclusion: In isolated porcine ciliary process es, beta-adrenergic receptor stimulation increases NO production.