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X. Zhang, A. Li, J. Ge, D. Reigada, A. M. Laties, C. H. Mitchell; Elevated ATP in Aqueous Humor of Patients With Acute Glaucoma. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4820.
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Glaucoma is typically characterized by an increase in intraocular pressure (IOP). Although an elevated pressure can lead to multiple changes in ocular tissues, the initial signals are not well understood. Throughout the body, the release of ATP transduces mechanical change into a neurochemical signal. This study sought to determine whether levels of ATP were elevated in the aqueous humor of patients with acutely elevated IOP.
ATP levels were determined with the luciferin-luciferase assay using aqueous humor samples collected from patients following the principals outlined by the Declaration of Helsinki. Samples were obtained from 14 patients undergoing an emergency anterior chamber paracentesis, a routine procedure following an acute attack of primary acute angle closure glaucoma at the Zhongshan Ophthalmic Center. Control samples were obtained from 18 cataract patients with normal IOP. IOP was measured using Goldmann tonometry. All samples were processed with respect for patient privacy following an accepted protocol. Rank Sum Test was used to analyze between two groups of ATP level and IOP level, respectively. Spearman Rank Correlation Analysis was used to evaluate the relationship between IOP and ATP levels.
The mean IOP of patients with primary acute angle closure glaucoma was 58.9±3.6 mm Hg, while that from controls was 13.2±0.4 mm Hg (p<0.001). The mean level of ATP in samples of aqueous humor were ten-fold higher in patients with primary acute angle closure glaucoma compared to control, being 224±36 pM in glaucomatous eyes and only 25±4 pM in control (p<0.001). The positive correlation between the magnitude of IOP elevation and ATP concentration was highly significant (Σ=0.83, p<0.001).
ATP levels are increased in the aqueous humor of patients with acute glaucoma in proportion to the rise in IOP. The cellular source of this ATP is unknown, although several cell types in the anterior eye are known to release ATP in response to swelling. The tight correlation between ATP and pressure suggests the rise results from controlled release, although cell lysis cannot be ruled out. It remains to be determined whether this excess ATP can initiate changes by stimulating local receptors.
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