CORNEAL ARACHIDONATE METABOLITES VIA CYTOCHROME P450

角膜的上皮细胞层可以被表征为角膜上皮细胞层。 “紧密”离子转运功能合胞体， 作为眼表的保护屏障，并作为辅助流体- 分泌层辅助角膜内皮细胞调节 基质水合作用，从而有助于 保持角膜透明。 输运性质 角膜上皮细胞类似于 亨利氏袢（TALH）的粗升支，肾单位 对于建立溶质梯度非常重要的部分， 通过氯化钠偶联转运的尿浓度。 两种转运上皮细胞都具有主动的氯离子转运偶联 Na ~+-K ~+激活的ATP酶。 最近，我们报道， TALH通过细胞色素代谢花生四烯酸（AA P450依赖性酶转化为两种生物活性代谢物： 一种抑制Na+-K+-ATP酶，另一种舒张血管。 观察到，野牡丹素和其他AA氧化 代谢物可作为转运过程的介质， 角膜上皮在离子方面与TALH相似 运输机制，引导我们调查 角膜中存在细胞色素P450依赖的AA代谢 上皮 我们的初步结果首次表明， 角膜上皮含有细胞色素P450物质 能够将AA代谢成几种化合物。 什么 这些化合物是否具有生物学效应， 细胞功能和离子转运是一些问题， 在这项研究中解决。 我们预计，根据平行研究， 肾脏的TALH，我们的工作将揭示 影响Na+-K+-ATP酶活性和血管反应性。 事实上，在最近的一项实验中，我们证明了一个人的能力， 角膜AA代谢产物抑制Na ~+-K ~+-ATP酶， 角膜 这种Na+-K+-ATP酶的内源性抑制剂 在角膜中合成的蛋白质可能对 依赖于这种泵机制的眼运输上皮细胞。 这些包括角膜上皮和内皮， 睫状体上皮、透镜囊下上皮和 视网膜色素上皮 此外，识别 促进血管舒张的内源性物质可 在生理学的不同领域都有重要意义， 病理生理学，如炎症机制， 眼循环和房水动力学。

The epithelial cell layers of the cornea can be characterized as a "tight" ion transporting functional syncytium which serves both as a protective barrier to the ocular surface, and as an adjunct fluid- secreting layer assisting the corneal endothelium in the regulation of stromal hydration and, thereby, contributing to the maintenance of corneal transparency. Transport properties of the corneal epithelium are similar to those of the epithelial cells of the thick ascending limb of Henle's loop (TALH), the nephron segment that is important for establishing the solute gradient for urinary concentration through sodium chloride coupled transport. Both transport epithelia possess active chloride transport coupled to Na+-K+-activated ATPase. Recently, we reported that cells of the TALH metabolized arachidonic acid (AA) by cytochrome P450-dependent enzyme(s) to two biologically active metabolites: one inhibits Na+-K+-ATPase and the other relaxes blood vessels. The observations that prostaglandins and other AA oxygenated metabolites may act as a mediator(s) of transport process, and the similarity of the corneal epithelium to TALH as regards ion transport mechanism, led us to investigate the possibility that the cytochrome P450-dependent AA metabolism exists in the corneal epithelium. Our preliminary results demonstrate for the first time that the epithelium of the cornea contains a cytochrome P450 species capable of metabolizing AA to several compounds. Exactly what these compounds are and whether they have biological effects on cell function and ion transport are questions which will be addressed in this study. We expect, based on parallel studies in the TALH of the kidney, that our work will reveal substances which affect Na+-K+-ATPase activity and vascular reactivity. Indeed, in a recent experiment we demonstrated the ability of one of the corneal AA metabolites to inhibit Na+-K+-ATPase of the cornea. Such an endogenous inhibitor of Na+-K+-ATPase synthesized in the cornea may have fundamental importance in ocular transport epithelia that rely on this pump mechanism. These include the corneal epithelium and endothelium, the epithelia of the ciliary body, the lens subcapsular epithelium and the retinal pigment epithelium. Furthermore, the identification of an endogenous substance which promotes vasodilatation may have significance in diverse areas of physiology and pathophysiology such as inflammatory mechanisms, control of the ocular circulation and aqueous humor dynamics.