β-Adrenergic agonist-induced nitrite production in isolated pig ciliary processes

Abstract 

· Background: We performed an experiment to assess whether in ciliary processes adrenergic-receptor agents can modulate the production of nitrite, an oxidized metabolite of nitric oxide (NO). · Methods: The porcine ciliary processes and the iris were dissected and stored at –20°C. Later, tissues were thawed, and nitrite measured by Griess reaction, before and 2 h after exposure to various drugs. · Results: In the ciliary processes, but not in the iris, the α-, β-adrenergic receptor agonist, norepinephrine (0.01–10 μM), increased nitrite production (95 ± 12%, P <0.01). The norepinephrine-induced (0.1 μM) nitrite production was inhibited by the inhibitor of NO synthase, Nω-nitro-L-arginine methyl ester (0.5 mM; P <0.05) and by the non-selective β-adrenergic receptor antagonist, propranolol (10 μM; P <0.01), but not by the non-selective α-adrenergic receptor antagonist, phentolamine (10 μM). · Conclusion: In isolated porcine ciliary processes, β-adrenergic receptor stimulation increases NO production.