title: Involvement of prostaglandin I(2) in nitric oxide-induced vasodilation of retinal arterioles in rats.
abstract: The soluble guanylyl cyclase/cGMP system plays an important role in the vasodilator response to nitric oxide (NO) in various vascular beds. However, in rat retinal arterioles, the cyclooxygenase-1/cAMP-mediated pathway contributes to the vasodilator effects of NO, although the specific prostanoid involved remains to be elucidated. In the present study, we investigated the role of prostaglandin I2 and its receptor (prostanoid IP receptor) system in NO-induced vasodilation of rat retinal arterioles in vivo. Fundus images were captured using a digital camera that was equipped with a special objective lens. Changes in diameter of retinal arterioles were assessed. The NO donor (±)-(E)-4-ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexenamide (NOR3) increased the diameter of retinal arterioles but decreased systemic blood pressure in a dose-dependent manner. Treatment of rats with indomethacin, a non-selective cyclooxygenase inhibitor, markedly attenuated the retinal vasodilator, but not depressor responses to NOR3. The prostanoid IP receptor antagonist 4,5-dihydro-N-[4-[[4-(1-methylethoxy)phenyl]methyl]phenyl]-1H-imadazol-2-amine (CAY10441), and the prostaglandin I2 synthase inhibitor 9α,11α-azoprosta-5Z,13E-dien-1-oic acid (U-51605), both showed similar preventive effects against the NOR3-induced retinal vasodilator response. Neither CAY10441 nor U-51605 showed any significant effects on the depressor response to NOR3. NOR3 enhanced the release of prostaglandin I2 from cultured human retinal microvascular endothelial cells and the NOR3-induced prostaglandin I2 release was almost completely abolished by the cyclooxygenase-1 inhibitor SC-560, but not by the cyclooxygenase-2 inhibitor NS-398. However, NOR3 did not increase the release of prostaglandin I2 from human intestinal microvascular endothelial cells. These results suggest that NO exerts its dilatory effect via cyclooxygenase-1/prostaglandin I2/prostanoid IP receptor signaling mechanisms in the retinal vasculature.
authors.affiliation: Department of Molecular Pharmacology, Kitasato University School of Pharmaceutical Sciences, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.
authors.forename: Asami
authors.initials: A
authors.lastname: Mori
authors.affiliation: Department of Molecular Pharmacology, Kitasato University School of Pharmaceutical Sciences, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Namekawa
authors.affiliation: Department of Molecular Pharmacology, Kitasato University School of Pharmaceutical Sciences, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.
authors.forename: Masami
authors.initials: M
authors.lastname: Hasebe
authors.affiliation: Department of Molecular Pharmacology, Kitasato University School of Pharmaceutical Sciences, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.
authors.forename: Maki
authors.initials: M
authors.lastname: Saito
authors.affiliation: Department of Molecular Pharmacology, Kitasato University School of Pharmaceutical Sciences, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Sakamoto
authors.affiliation: Department of Molecular Pharmacology, Kitasato University School of Pharmaceutical Sciences, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan. Electronic address: nakaharat@pharm.kitasato-u.ac.jp.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Nakahara
authors.affiliation: Department of Molecular Pharmacology, Kitasato University School of Pharmaceutical Sciences, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.
authors.forename: Kunio
authors.initials: K
authors.lastname: Ishii
mesh_terms: D000818:Animals; D001160:Arterioles / Q000187:drug effects / Q000502:physiology*; D001593:Benzyl Compounds / Q000494:pharmacology; D002478:Cells, Cultured; D051545:Cyclooxygenase 1 / Q000502:physiology; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D042783:Endothelial Cells / Q000378:metabolism; D011464:Epoprostenol / Q000502:physiology*; D006801:Humans; D006898:Hydroxylamines / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D008297:Male; D009569:Nitric Oxide / Q000502:physiology; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009574:Nitro Compounds; D009578:Nitrobenzenes / Q000494:pharmacology; D011463:Prostaglandins H / Q000494:pharmacology; D011720:Pyrazoles / Q000494:pharmacology; D017208:Rats, Wistar; D011982:Receptors, Prostaglandin / Q000037:antagonists & inhibitors / Q000502:physiology; D012171:Retinal Vessels / Q000187:drug effects / Q000502:physiology*; D013449:Sulfonamides / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects
chemical_list: C514222:(2-(4-(4-isopropoxybenzyl)-phenylamino) imidazoline); D001593:Benzyl Compounds; D016861:Cyclooxygenase Inhibitors; D006898:Hydroxylamines; D007093:Imidazoles; D020030:Nitric Oxide Donors; D009574:Nitro Compounds; D009578:Nitrobenzenes; D011463:Prostaglandins H; D011720:Pyrazoles; D011982:Receptors, Prostaglandin; C115461:SC 560; D013449:Sulfonamides; C080955:N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide; D009569:Nitric Oxide; C015014:azo analog I; C061872:FK 409; D011464:Epoprostenol; D051545:Cyclooxygenase 1
keywords: Cyclooxygenase; Nitric oxide; Prostaglandin I(2); Prostanoid IP receptor; Retinal blood vessel