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Hoi Lam Li, Nicole E. Ashpole, Iris D Navarro, Thomas C Lam, Ho Lung Henry Chan, Chi Ho To, W Daniel Stamer, Chi-wai Do; Baicalein lowers intraocular pressure and increases outflow facility in mouse eye. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4853. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Baicalein is a natural flavonoid derived from the root of Scutellaria baicalensis. We have previously demonstrated that intraperitoneal administration of baicalein lowers intraocular pressure (IOP) in rodents. In this study, we aimed to investigate whether 1) similar ocular hypotensive effects were observed after topical application rather than intraperitoneal injection; and 2) baicalein altered the outflow facility using freshly enucleated mouse eyes.
Adult C57BL/6J (B6) mice were used. Intraocular pressure (IOP) was measured by rebound tonometry under awake condition. Topical baicalein (20 µL, 10 mM) was applied to the treatment eye twice separated by 10-min intervals while phosphate buffered saline (PBS) was used in the fellow eye as control. IOP measurements were conducted before and after drug administration (i.e. 1.5, 3, 6, 24, 48 and 72 h) in both light and dark phases. The outflow facility was determined by measuring the flow rates at sequential pressure steps (i.e. 4, 8, 12, 16 and 20 mmHg) in freshly enucleated mice eyes. Comparisons were made between the baicalein-treated and vehicle-treated contralateral eye of the same animal.
Topical administration of 10 mM baicalein caused significant IOP reduction within 6 hours after drug treatment. The maximum IOP-lowering effect was 1.44±0.25 (n = 23, p < 0.01) and 2.16±0.37 (n = 23, p < 0.01) mmHg under light and dark conditions, respectively. In addition, 10µM baicalein significantly enhanced the outflow facility in paired mouse eyes (n = 4, p < 0.05). The outflow facility of baicalein-treated and control eyes were 0.041±0.010 and 0.021±0.005 µL/min/mmHg, respectively.
Topical application of baicalein triggered a transient IOP reduction although its effect was smaller than that of intraperitoneal injection. The ocular hypotensive effect was mediated, at least in part, by the facilitation of aqueous outflow. The precise mechanism of action remains to be determined.
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