Crook R B, Song M K, Tong L P, Yabu J M, Polansky J R, Lui G M
Department of Ophthalmology, University of California, San Francisco 94143.
Brain Res. 1992 Jun 26;583(1-2):23-30. doi: 10.1016/s0006-8993(10)80006-x.
Several hormones, neurotransmitters, and neuropeptides were screened for the ability to stimulate inositol phosphate formation in cultured human retinal epithelial (RPE) cells. Carbachol, vasopressin and thrombin were found to be effective. Treatment of RPE cells with all three agents produced increases in inositol monophosphate, inositol bisphosphate and inositol trisphosphate in the presence of 10 mM LiCl. Carbachol stimulated a 4-fold increase in the total of inositol phosphates at 1 mM. Studies with cholinergic antagonists showed a rank order of 4 DAMP greater than QNX greater than pirenzepine greater than methoctramine, suggesting the presence of M3 muscarinic receptors. Vasopressin gave a 2.5-fold stimulation at 10 microM. Agonists of vasopressin were also tested and gave differential responses. Studies using a V1 agonist (PIOVP) and a V2 agonist (DAVP) showed DAVP matching the level of stimulation elicited by vasopressin whereas treatment with PIOVP only reached 50% of the vasopressin response. These data suggested the presence of V2 receptors in the RPE cells. Several proteases were tested for their ability to stimulate RPE inositol phosphates. Thrombin caused a 7-fold increase in inositol phosphate formation at 1 U/ml, whereas trypsin and plasmin elicited smaller responses (approximately 2-fold). The thrombin effect was blocked by the thrombin-specific inhibitor, hirudin, but not by other protease inhibitors. Several mediators of inflammation such as bradykinin, histamine and serotonin were also tested, and they were ineffective in stimulating inositol phosphate turnover in the RPE cells.
对几种激素、神经递质和神经肽进行了筛选，以检测它们刺激培养的人视网膜色素上皮（RPE）细胞中肌醇磷酸形成的能力。发现卡巴胆碱、血管加压素和凝血酶具有此作用。在10 mM LiCl存在的情况下，用这三种试剂处理RPE细胞均使单磷酸肌醇、二磷酸肌醇和三磷酸肌醇增加。卡巴胆碱在1 mM时可使肌醇磷酸总量增加4倍。胆碱能拮抗剂研究显示，4-DAMP＞QNX＞哌仑西平＞甲溴东莨菪碱，提示存在M3毒蕈碱受体。血管加压素在10 μM时刺激作用为2.5倍。还测试了血管加压素激动剂并得到不同反应。使用V1激动剂（苯赖加压素）和V2激动剂（去氨加压素）的研究显示，去氨加压素的刺激水平与血管加压素相当，而用苯赖加压素处理仅达到血管加压素反应的50%。这些数据提示RPE细胞中存在V2受体。测试了几种蛋白酶刺激RPE细胞肌醇磷酸形成的能力。凝血酶在1 U/ml时可使肌醇磷酸形成增加7倍，而胰蛋白酶和纤溶酶引起的反应较小（约2倍）。凝血酶的作用被凝血酶特异性抑制剂水蛭素阻断，但不被其他蛋白酶抑制剂阻断。还测试了几种炎症介质如缓激肽、组胺和5-羟色胺，它们对刺激RPE细胞中肌醇磷酸周转无效。
