Isoproterenol, forskolin, and cAMP-induced nitric oxide production in pig ciliary processes.
OBJECTIVE
To investigate whether isoproterenol and forskolin, two adenylylcyclase activators, or 8-bromo-cAMP, an adenosine 3',5'-cyclic monophosphate (cAMP) analog, increase nitric oxide (NO) production in isolated porcine ciliary processes.


METHODS
Nitrite (an NO metabolite) was measured (Griess reaction) before and 2 hours after exposure to 0.1 to 100 microM isoproterenol (a beta-adrenoreceptor agonist), 0.01 to 100 microM forskolin, or 0.1 to 1000 microM 8-bromo-cAMP. Some experiments were conducted in the presence of 0.5 mM N(G)-nitro-L-arginine methyl ester (L-NAME; a nitric oxide synthase [NOS] inhibitor), 10 microM propranolol (a beta-adrenoreceptor antagonist), or 1 microM KT 5720 (a cAMP-dependent protein kinase inhibitor). cAMP production was also measured (by immunoassay).


RESULTS
Nitrite production was increased by isoproterenol (maximum, 10 microM: 164%; P < 0.001), forskolin (maximum, 10 microM: 254%; P < 0.001), and 8-bromo-cAMP (maximum, 100 microM: 184%; P < 0.001), an effect prevented by L-NAME (P < 0.05-0.001). Propranolol inhibited only isoproterenol-induced (10 microM) nitrite production (P < 0.05), whereas KT 5720 (P < 0.05) inhibited isoproterenol- (10 microM) and 8-bromo-cAMP-induced (10 microM) nitrite production. Furthermore, cAMP production evoked by isoproterenol (10 microM, P < 0.05) but not by forskolin (10 microM, P < 0.001) was inhibited by propranolol (P < 0.05).


CONCLUSIONS
In isolated porcine ciliary processes, drugs activating adenylylcyclase or mimicking cAMP increase the production of NO by a mechanism that appears to involve both a cAMP-dependent protein kinase and NOS.
Laboratory of Ocular Pharmacology and Physiology, University Eye Clinic, Basel, Switzerland.
R
R
Liu
J
J
Flammer
I O
IO
Haefliger
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology*; D000262:Adenylyl Cyclases / Q000378:metabolism; D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D002924:Ciliary Body / Q000187:drug effects* / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D013552:Swine
D000318:Adrenergic beta-Agonists; D004791:Enzyme Inhibitors; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D017868:Cyclic AMP-Dependent Protein Kinases; D000262:Adenylyl Cyclases; D007545:Isoproterenol; D019331:NG-Nitroarginine Methyl Ester