Real-time direct measurement of nitric oxide in bovine perfused eye trabecular meshwork using a Clark-type electrode

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Abstract

NO was detected in bovine trabecular meshwork (TM). Bovine eyes were perfused (posterior ciliary artery). In some eyes (operated eyes) a NO electrode was inserted adjacent to the TM (scleral flap). Vascular perfusion/intraocular pressures (VPP/IOP) were recorded. In operated eyes, epinephrine (1 nM-100 μM) increased NO (maximally 979.9 ± 117.6 nM, mean ± SDM). Timolol (1 mM) shifted the epinephrine-NO concentration-response curve rightward (2.94 log units) without significantly changing the maximal response (903.0 ± 67.7 nM, mean ± SDM). The non-selective NO synthase (NOS) inhibitor L-NMMA (100 μM) virtually abolished the NO response to epinephrine. L-NMMA alone (1 μM-100 μM) significantly reduced tonic NO generation (maximally 109.5 ± 24.9 nM, mean ± SDM), whereas timolol alone (1 μM-1 mM) had no effect. In unoperated eyes, epinephrine (1 nM-100 μM) reduced IOP (maximally 2.56 ± 0.64 mmHg, mean ± SDM). Epinephrine (100 μM) mildly increased VPP (4.6 ± 1.3 mmHg, mean ± SDM). Baseline aqueous humor formation rate (11.5 ± 3.2 μl/min, mean ± SDM) was unaffected. Effluent perfusate (effusate) total NO2- was determined by enzymatically reducing all NO3- to NO 2-, then assessing resultant NO2- (Griess assay). Epinephrine (1 nM-100 μM) increased effusate NO 2- (maximally 15.8 ± 4.9 μM, mean ± SDM). Timolol (1 mM) reduced, and L-NMMA (100 μM) virtually abolished effusate NO2- response to epinephrine. L-NMMA alone (1 μM-100 μM) reduced tonic effusate NO2- (maximally from 5.8 ± 1.6 μM to 1.1 ± 0.9 μM, mean ± SDM), whereas timolol alone (1 μM-1 mM) had no effect. NO is generated tonically in bovine TM and increases in response to epinephrine.

Original languageEnglish
Pages (from-to)299-313
Number of pages15
JournalJournal of Ocular Pharmacology and Therapeutics
Volume19
Issue number4
DOIs
StatePublished - 1 Jan 2003

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