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Abstract #9672 Published in IGR 5-3
Real-time direct measurement of nitric oxide in bovine perfused eye trabecular meshwork using a Clark-type electrode
Millar JCJournal of Ocular Pharmacology and Therapeutics 2003; 19: 299-313
Nitric oxide (NO) was detected in bovine trabecular meshwork (TM). Bovine eyes were perfused (posterior ciliary artery). In some eyes (operated eyes) an 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 (1-100 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 NO2-, 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 (1-100 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.
Dr. J.C. Millar, In Vivo Pharmacology, Alcon Research, Ltd., 6201 South Freeway, Fort Worth, TX 76134-2099, USA
Classification:
2.5.1 Trabecular meshwork (Part of: 2 Anatomical structures in glaucoma > 2.5 Meshwork)
3.20 Other (Part of: 3 Laboratory methods)
