Original Paper Ophthalmic Res 2002;34:90–93 Received: June 7, 2001 Accepted: September 26, 2001 Effects of Isopropyl Unoprostone, Latanoprost, and Prostaglandin E2 on Acute Rise of Aqueous Flare in Pigmented Rabbits Xue-Yun Zhang Seiji Hayasaka Yoriko Hayasaka Shuichiro Yanagisawa Yasunori Nagaki Department of Ophthalmology, Toyama Medical and Pharmaceutical University, Toyama, Japan Abstract Purpose: To evaluate the effect of isopropyl unoprostone, latanoprost, and prostaglandin E2 (PGE2) on aqueous flare elevation. Methods: Isopropyl unoprostone (0.12%) or latanoprost (0.005%) was topically instilled. Transcorneal diffusion of PGE2, 25 Ìg/ml, using a glass cylinder, was achieved in pigmented rabbits. Aqueous flare was measured with a laser flare cell meter. Results: Topical instillation of isopropyl unoprostone induced aqueous flare elevation in rabbit eyes. Also, topical isopropyl unoprostone additionally induced aqueous flare elevation in eyes with transcorneal diffusion of PGE2. Latanoprost did not induce flare elevation. Conclusion: Isopropyl unoprostone induced aqueous flare elevation in rabbits, and latanoprost did not produce aqueous flare elevation. Copyright © 2002 S. Karger AG, Basel Studies from our laboratory previously reported that transcorneal diffusion of prostaglandin E2 (PGE2) using a glass cylinder induced aqueous flare elevation in pigmented rabbits, and that the elevation was reproducible ABC © 2002 S. Karger AG, Basel 0030–3747/02/0342–0090$18.50/0 Fax + 41 61 306 12 34 E-Mail email@example.com www.karger.com Accessible online at: www.karger.com/journals/ore when PGE2 was applied at an interval of more than 1 week [1, 2]. We also reported that topical instillation of betaxolol, an antiglaucoma agent, inhibited PGE2-induced aqueous flare elevation in pigmented rabbits . PGF2· analogues such as isopropyl unoprostone and latanoprost are commercially available as antiglaucoma agents. Some investigators compared the effects of these compounds in human subjects [4–6]. Linder et al.  and Widergard et al.  have reported that latanoprost had no clinically significant effect on the permeability of the blood-aqueous barrier in humans. Others have described anterior uveitis or disruption of the blood-aqueous barrier associated with latanoprost [9–12]. In the present study, we examined the effects of isopropyl unoprostone, latanoprost, and PGE2 on aqueous flare elevation in pigmented rabbits. Materials and Methods Animals A total of 32 pigmented male rabbits (Japanese mongrel) that weighed 2.5–3.5 kg each were used. The animals were housed and treated according to the Association for Research in Vision and Ophthalmology (USA) Resolution on Use of Animals in Research. One eye of each animal was used for the experiment. Chemicals PGE2 was obtained from Funakoshi Chemicals (Tokyo, Japan). PGE2 was dissolved in 100% ethanol and stocked at –70 ° C. PGE2 Xue-Yun Zhang, PhD Department of Ophthalmology Toyama Medical and Pharmaceutical University 2630 Sugitani, Toyama 930-0194 (Japan) Tel. +81 76 434 7363, Fax +81 76 436 0146 Downloaded by: University of Missouri-Columbia 22.214.171.124 - 10/26/2017 1:10:05 PM Key Words Aqueous flare W Isopropyl unoprostone W Latanoprost W Prostaglandin E2 W Rabbit Fig. 1. Changes in flare intensity following topical instillation of isopropyl unoprostone. $ = Two instillations (–30 and 0 min) of 0.12% isopropyl unoprostone; ) = one instillation. The mean B standard deviation (n = 4) is shown. Fig. 2. Changes in flare intensity following transcorneal diffusion of PGE2 with or without topical instillation of isopropyl unoprostone. P = Transcorneal application of PGE2, 7.09 ! 10 –2 mmol/l, for 4 min (black arrow); [ = 0.12% isopropyl unoprostone was topically instilled 60 and 30 min before PGE2 application (white arrows). The mean value B standard deviation (n = 4) is shown. solution was diluted to 5% ethanol with 0.9% NaCl just before use. Isopropyl unoprostone, 0.12%, ophthalmic solution (Rescula) was obtained from Fujisawa Pharmaceutical Company (Osaka, Japan). Latanoprost, 0.005%, ophthalmic solution (Xalatan) was purchased from Pharmacia Upjohn Company (Tokyo, Japan). Statistics Statistical analysis was performed using Scheffe’s procedure for multiple comparisons of means. A probability (p) value less than 0.05 was considered significant. Results Aqueous Flare Measurement Aqueous flare was measured with a laser flare cell meter (FC 1000, Kowa, Tokyo, Japan), according to the method described by Sawa et al. . A laser flare cell meter measured intracameral proteins. Five measurements were taken at each time point to obtain the mean value. The measurement was taken in the midportion of the anterior chamber. The sampling area was 0.075 mm2. Aqueous flare elevation was expressed as the area under the curve (AUC) in arbitrary units. The person taking the measurements had no knowledge of the treatment. No remarkable changes in the systemic conditions were noted following topical instillation of isopropyl unoprostone or latanoprost, or transcorneal diffusion of PGE2. Topical instillation of 0.9% NaCl or 0.005% latanoprost had no effect on aqueous flare. After topical instillation of isopropyl unoprostone, aqueous flare increased, peaked at 1.5–2 h, and returned to the baseline level at 7–8 h (fig. 1). Two instillations of 0.12% isopropyl unoprostone showed higher elevation than one instillation. Transcorneal diffusion of 0.5% ethanol had almost no effect on aqueous flare. After transcorneal diffusion of PGE2, aqueous flare increased, reached its maximum at 60–120 min, and then gradually decreased and returned to the baseline level at 8 h (fig. 2). Topical isopropyl unoprostone induced additional aqueous flare elevation. Effects of topical instillation of isopropyl unoprostone or latanoprost and transcorneal diffusion of PGE2 are PGF2· Analogues and Aqueous Flare Ophthalmic Res 2002;34:90–93 Transcorneal Diffusion of PGE2 or 5% Ethanol For transcorneal diffusion, a glass cylinder (11 mm in diameter) was attached to one eye, as described previously . A total of 600 Ìl of PGE2 solution, 25 Ìg/ml, or 5% ethanol was delivered into the cylinder and pipetted out 4 min later. The cylinder was removed, and the corneal surface and conjunctival sac were rinsed with 20 ml of 0.9% NaCl. 91 Downloaded by: University of Missouri-Columbia 126.96.36.199 - 10/26/2017 1:10:05 PM Topical Instillation of NaCl, Isopropyl Unoprostone, or Latanoprost 50 Ìl of 0.9% NaCl, 0.12% isopropyl unoprostone, or 0.005% latanoprost was topically instilled in one eye. The instillation took place twice (60 and 30 min before 0.5% ethanol or PGE2), or once (30 min before 0.5% ethanol or PGE2). latanoprost, and PGE2 on aqueous flare elevation in pigmented rabbits Topical instillation Times1 Transcorneal diffusion Eyes NaCl, 0.9% Isopropyl unoprostone, 0.12% 2 2 1 2 ethanol, 5% ethanol, 5% ethanol, 5% ethanol, 5% 4 4 4 4 18B15 670B81 307B32 17B11 2 2 1 2 PGE2, 25 Ìg/ml PGE2, 25 Ìg/ml PGE2, 25 Ìg/ml PGE2, 25 Ìg/ml 4 4 4 4 1,325B201 1,947B260 1,612B215 1,240B170 Latanoprost, 0.005% NaCl, 0.9% Isopropyl unoprostone, 0.12% Latanoprost, 0.005% 1 2 ** ** ** NS ** ** ** NS ** p ! 0.01; NS, p 1 0.05. Once, 60 min before ethanol or PGE2; twice, 60 and 30 min before ethanol or PGE2. AUC (arbitrary units), means B SD. shown in table 1. Topical instillation of isopropyl unoprostone induced aqueous flare elevation that was dependent on the number of instillations. The AUC (1,974 units) following two instillations of isopropyl unoprostone and transcorneal PGE2 was quite similar to the summation of the AUC (670 units) following two instillations of isopropyl unoprostone and the AUC (1,325 units) following transcorneal PGE2. Latanoprost had no effect on PGE2-induced aqueous flare elevation. Discussion Aqueous flare elevation, mean B standard deviation, following transcorneal PGE2 using a glass cylinder in the present study was similar to that observed in our previous study . In the present study, isopropyl unoprostone induced aqueous flare elevation in the rabbit eye. Sakurai et al.  previously showed that the rabbit bloodaqueous barrier was disrupted after instillation of isopropyl unoprostone, using fluorescein isothiocyanate-labeled rabbit albumin. Our data obtained using a laser flare cell meter were quite similar to the findings of Sakurai et al. . Isopropyl unoprostone induced additional aqueous flare elevation in eyes with transcorneal diffusion of PGE2. Some investigators have reported that latanoprost induced anterior uveitis or flare elevation in humans [9– 12]: Fechtner et al. , Warwar et al.  and Smith et al.  contributed case reports, whereas Miyake et al.  described an experimental situation following cataract surgery. However, controlled clinical studies showed that 92 Flare elevation2 p value Ophthalmic Res 2002;34:90–93 inflammation was not associated with latanoprost in humans [7, 8]. Yousufzai et al.  reported that exogenous latanoprost stimulated the formation of PGE2, PGD2, and PGF2· in iris and ciliary body muscles isolated from cats, cattle, rabbits, dogs, rhesus monkeys and humans. In the present study, however, latanoprost did not induce flare elevation in rabbit eyes with or without transcorneal diffusion of PGE2. This discordance may possibly be due to differences between in vitro (isolated tissue) versus in vivo experiments and measurements (PGs versus flare intensities). Species differences in the response of the eye to irritation and trauma have been demonstrated . The bloodaqueous barrier in rabbits has unique sensitivity to PGs . The blood-aqueous barrier may be more labile in rabbits than in humans. Isopropyl unoprostone induced aqueous flare elevation in rabbits. Zhang/Hayasaka/Hayasaka/Yanagisawa/ Nagaki Downloaded by: University of Missouri-Columbia 188.8.131.52 - 10/26/2017 1:10:05 PM Table 1. Effect of isopropyl unoprostone, References PGF2· Analogues and Aqueous Flare 7 Linden C, Nuija E, Alm A: Effects of IOP restoration and blood-aqueous barrier after long term treatment with latanoprost in open angle glaucoma and ocular hypertension. 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