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Z. Si, A. Palkama, B.M. Gebhardt, R.W. Beuerman; Effect of Latanoprost on Outflow Facility and Protein Liberation in the Bovine Eye In Vitro . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1153.
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Purpose: To investigate the effect of latanoprost on outflow facility and protein release, especially thrombospondin-4 (TSP-4), in perfused bovine anterior segments. Methods: The segments were attached to a perfusion chamber. Group-1 eyes were perfused at 11 mm Hg, 34° C, for 18 h with 5 nM latanoprost in DMEM+PSA (controls, no drug). Outflow facility µl/min/mmHg) was measured continuously with an electronic balance. Group-2 eyes were immersed in silicone oil and perfused at 4°C for 72 h. Effluent was collected on the surface of the oil over 4 intervals: 0-4, 4-24, 24-48, 48-72 h. Outflow facility was measured and protein composition and concentration analyzed (SDS-PAGE, Western blot) in the effluent and tissue samples from site 1 (limbal area above trabecular meshwork) and site 2 (sclera 1-2 mm posterior to limbus with aqueous ducts). Differences were analyzed by 2-tailed Student’s t-test or ANOVA. TSP-4 distribution was determined by indirect immunohistochemistry. Results: Group-1: Overall mean outflow facility was significantly higher in latanoprost-treated eyes vs controls (1.41±0.18, n=11 vs 0.88±0.10, n=18; P=0.007). Group-2: Overall outflow facility was 0.61±0.07 (n=14) in latanoprost-treated eyes and 0.46±0.07 (n=18) in controls. Only in the first 4 h was outflow facility significantly higher in the drug-treated eyes vs controls (0.86±0.09 vs 0.58±0.09, P<0.05). Immunoblotting to anti-TSP-4 produced a 110-kDa band in effluent and tissues; density in the effluent was lower in the latanoprost-treated eyes vs controls (1.9±1.1 µg/ml, n=5, vs 4.2±1.2 µg/ml, n=5). Compared with fresh, non-perfused tissue from site 1, concentrations of the 110-kDa fragment of TSP-4 were 28% lower in the latanoprost-perfused samples and 51% lower (P<0.05) in controls. At site 2, concentrations were 32% higher with drug and 4% lower without, vs fresh tissue. The amount of a 65-kDa protein (albumin) in the effluent was higher in latanoprost-treated eyes vs controls (127.6±21.0 µg/ml, n=5 vs 114.1±16.3 µg/ml, n=5). The 65 kDa protein was78% lower at site 1 and 81% lower at site 2 in the drug-perfused tissues (P=0.0001, n=10), and 60% and 20% lower at site 1 and site 2 in the controls (P=0.2, n=9), compared with fresh samples. None of the perfused eyes, with/without drug, showed immunohistochemical changes in the TSP-4 reaction in the trabecular meshwork or aqueous ducts. Conclusion: The prostaglandin derivative, latanoprost, significantly increased outflow facility in perfused bovine eyes. Latanoprost prevented the release of TSP-4 from the outflow pathways, especially distally, while enhancing the release of albumin.
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