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Caroline Manicam, Julia I Staubitz, Norbert Pfeiffer, Adrian Gericke; Mechanisms of Endothelium-Dependent Vasodilation in the Ophthalmic Artery of Mice. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4350.
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© ARVO (1962-2015); The Authors (2016-present)
To identify the mechanisms of endothelium-dependent vasodilation in the ophthalmic artery of mice.
Ophthalmic arteries from mice (C57/BL6J) were studied in vitro. Changes in artery luminal diameter in response to the endothelium-dependent vasodilator acetylcholine were measured using video microscopy.
Acetylcholine (10-9-10-4 M) induced concentration-dependent vasodilation in ophthalmic arteries. The non-isoform-selective nitric oxide synthase (NOS) inhibitor, L-NGnitro arginine methyl ester (L-NAME) (10-4 M), reduced acetylcholine-induced vasodilation by about 50%. Blockade of the nitric oxide receptor, soluble guanylate cyclase, by 1H-(1,2,4) oxadiazole (4,3-alpha)quinoxaline-1-one (ODQ) (10-5 M) reduced vasodilation to acetylcholine by about 50%. Cyclooxygenase (COX) inhibition by indomethacin (10-5 M) did not affect acetylcholine-induced vasodilation. Combined blockade of NOS and COX with L-NAME (10-4 M) and indomethacin (10-5 M) reduced vasodilation respones to acetylcholine by about 50%, similar to blockade with L-NAME alone, and the residual response was abolished by addition of 30 mM KCl, indicative of the involvement of endothelium-dependent hyperpolarizing factors (EDHFs). To identify the EDHFs involved, we examined ophthalmic artery responses before and after incubation with catalase to test the involvement of hydrogen peroxide, 17-octadecynoic acid (17-ODYA), an inhibitor of CYP450 oxygenase, baicalein, a lipoxygenase inhibitor, and 18-alpha glycyrrhetinic acid (18-alpha GA), a gap junction blocker. Catalase had no effect on cholinergic vasodilation. However, 17-ODYA, baicalein, and 18-alpha GA markedly blocked vasodilation responses to acetylcholine.
Our data suggest that acetylcholine-induced vasodilation in the mouse ophthalmic artery is mediated in part by NO and in part by EDHFs. The EDHFs appear to be CYP450 oxygenase and lipoxygenase products and involve the GAP junction activation.
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