PLATELET ACTIVATING FACTOR AND THROMBOXANES IN LIVER

血小板活化因子（PAF）和血栓素A2（TxA 2）是一种有效的 急性过敏和炎症反应的脂质化学介质。 最近，我们观察到AGEPC（合成PAF）和U-46619（a TxAs 模拟专家强大的刺激作用，对糖原分解灌注 通过间接机制，包括肝收缩， 脉管系统肝血管的收缩发生在急性 过敏反应和PAF和TxA 2由炎性细胞产生 并在免疫挑战期间存活。 因此，PAF和TxA 2可能在血小板活化过程中起重要作用。 在调节肝血流和供应中的潜在重要作用 在病理生理状态下，肝外组织中的葡萄糖。 本研究的主要目的是阐明PAF的roe， TxA 2对肝血流动力学和糖原分解的影响， 深入了解这些脂质介质的分子基础， 肝内皮细胞和枯否细胞，它们调节通过 肝血窦 体内实验将表征 硒介质对肝血流动力学影响 门静脉压力和肝门静脉和动脉流量。 同时 将进行测量以评价肝糖原分解， 在这些实验条件下的血糖浓度。 最后，我们将评估PAF和TxA 2作为介导剂的作用， 病理生理过程中肝脏血流动力学和糖原分解变化 situations. 表征相关肝受体的实验 在这些脂质激动剂的血流动力学反应中， 灌注的肝脏和肝内皮细胞和枯否细胞。 放射配 与PAF和TxA 2受体的结合及受体参与的机制 将探索内皮细胞和枯否细胞中的信号转导。 我们的初步实验表明这些受体与 枯否细胞胞浆游离钙浓度（[Ca 2 +]i）的变化 细胞，并与AGEPC受体，刺激磷酸肌醇特异性 脂酶C已 这些脂质激动剂对[Ca 2 +]i的影响将是 通过Fura 2负载细胞的数字图像分析表征， 与对磷脂酶C的活化和 Ca 2+调节第二信使。 蛋白激酶C和鸟嘌呤的作用 受体介导的生物信号中的核苷酸调节蛋白将是 探讨了 将在效力的等级顺序之间进行相关性， 对肝血管收缩，受体结合， [Ca2=]i和磷脂酶C。 这项研究将提供新的 深入了解PAF和TxA 2在肝脏中的作用机制， 希望这将有助于更准确地了解他们的 在其他非肝细胞和组织中的作用。

Platelet activating factor (PAF) and thromboxane A2 (TxA2) are potent lipid chemical mediators of acute allergic and inflammatory responses. Recently, we observed that AGEPC (synthetic PAF) and U-46619 (a TxAs analog expert powerful stimulatory effects on glycogenolysis in perfused rat livers by an indirect mechanism involving constriction of the hepatic vasculature. Constriction of the hepatic vasculature occurs during acute allergic reactions and PAF and TxA2 are produced by inflammatory cells and live during immune challenge. Thus, PAF and TxA2 may play a potentially important role in regulating hepatic blood flow and supplying extrahepatic tissues with glucose during pathophysiological states. The major objectives of this study are to elucidate the roe of PAF and TxA2 on hepatic hemodynamics and glycogenolysis in vivo and to provide insight into the molecular basis of action of these lipid mediators in hepatic endothelial and Kupffer cells, which regulate flow through the hepatic sinusoids. Experiments in vivo will characterize the effects of the se mediators on hepatic hemodynamics by measurements of hepatic portal pressure and hepatic portal and arterial flows. Simultaneous measurements will be performed to evaluate hepatic glycogenolysis and blood glucose concentrations under these experimental conditions. finally, we will assess the role of PAF and TxA2 as mediators of hemodynamic and glycogenolytic changes in liver during pathophysiologic situations. Experiments to characterize the hepatic receptors involved in hemodynamic responses to these lipid agonists will be performed in perfused livers and hepatic endothelial and Kupffer cells. Radioligand binding to PAF ad TxA2 receptors and mechanisms involved in receptor signal transduction in endothelial and Kupffer cells will be explored. Our preliminary experiments suggest these receptors are coupled to changes in cytosolic free calcium concentrations ([Ca2+]i) in Kupffer cells and, with AGEPC receptors, stimulation of phosphoinositide-specific phospholipase C. Effects of these lipid agonists on [Ca2+]i will be characterized by digital image analysis of Fura 2-loaded cells and compared to effects on activation of phospholipase C and production of Ca2+-regulating second messengers. Roles of protein kinase C and guanine nucleotide regulatory proteins in receptor-mediated biosignalling will be explored. Correlations will be made between rank order of potencies of agonists and antagonists on hepatic vasoconstriction, receptor binding, [Ca2=]i and phospholipase C. The proposed study will provide new insights into the mechanisms of action of PAF and TxA2 in liver and hopefully will contribute to a more precise understanding of their actions in other non-hepatic cells and tissues.