Localization of lipocalin-type prostaglandin D synthase (beta-trace) in iris, ciliary body, and eye fluids.

PURPOSE Prostaglandin (PG) D synthase is present in neural tissues and cerebrospinal fluid (beta-trace). This enzyme belongs to the lipocalin family which consists of transporter proteins for lipophilic substances in the extracellular space. PGD synthase is found in retinal pigment epithelium, from where it is secreted into the interphotoreceptor matrix. The authors have undertaken the localization of this unique enzyme within the tissues and spaces of the anterior segment of the eye. METHODS Iris, ciliary body, lens, and aqueous and vitreous humors were collected from adult rats and mice. PGD synthase activity was determined, and the protein was quantified by Western blot analysis and localized immunohistochemically. Finally, in situ hybridization was performed to localize PGD synthase mRNA. RESULTS PGD synthase was most abundant in the aqueous and vitreous humors. It was less abundant in tissue cytosolic fractions; these fractions had almost 10-fold as much as their corresponding membrane-bound fractions. Lens tissue had the lowest amount observed. PGD synthase was localized to the epithelial cells of the iris and the ciliary body and to the adjacent extracellular chambers, but PGD synthase mRNA was found only within the epithelial cells. Several glycosylated forms of PGD synthase were also detected. CONCLUSIONS PGD synthase was synthesized within the epithelial cells of the iris and the ciliary body and was then secreted into the aqueous and vitreous humors, where it accumulated as an active enzyme.

目的 前列腺素（PG）D合酶存在于神经组织和脑脊液（β -痕迹蛋白）中。这种酶属于脂质运载蛋白家族，该家族由细胞外空间中亲脂性物质的转运蛋白组成。PGD合酶存在于视网膜色素上皮中，并从那里被分泌到光感受器间基质中。作者对这种独特的酶在眼前段的组织和间隙内进行了定位。 方法 从成年大鼠和小鼠收集虹膜、睫状体、晶状体以及房水和玻璃体液。测定PGD合酶活性，并通过蛋白质印迹分析对该蛋白质进行定量以及通过免疫组织化学方法进行定位。最后，进行原位杂交以定位PGD合酶mRNA。 结果 PGD合酶在房水和玻璃体液中含量最丰富。在组织胞质组分中含量较少；这些组分的含量几乎是其相应膜结合组分的10倍。在晶状体组织中观察到的含量最低。PGD合酶定位在虹膜和睫状体的上皮细胞以及相邻的细胞外腔室，但PGD合酶mRNA仅在 epithelial cells（上皮细胞）内被发现。还检测到了几种糖基化形式的PGD合酶。 结论 PGD合酶在虹膜和睫状体的上皮细胞内合成，然后被分泌到房水和玻璃体液中，在那里它作为一种活性酶积累。