The studies for expression and secretion of adrenomedullin and its signal transduction.

肾上腺髓质素（Adrenomedulin，AM）是新近从人嗜铬细胞瘤组织中分离到的一种强血管舒张肽，其结构属于CGRP家族。AM mRNA在心、肺、肾、血管壁及肾上腺髓质等多种组织中均有高表达。本课题通过测定心力衰竭大鼠血浆肾上腺髓质素（adrenomedullin，AM）水平及不同组织中AM肽和mRNA水平，探讨AM在心力衰竭时的产生和分泌部位。我们还检查了心力衰竭患者的心脏是否真的分泌AM进入循环。心力衰竭大鼠血浆AM水平升高，与心室重量相关。心力衰竭大鼠心、肺组织中AM肽和mRNA水平升高，而肾、肾上腺组织中AM肽和mRNA水平无明显变化。高血压患者冠状窦血浆AM水平高于主动脉， ...更多信息 心脏衰竭这些结果表明，血浆肾上腺髓质素水平增加心力衰竭的严重程度成比例，心脏的生产和分泌的肾上腺髓质素增加心力衰竭大鼠。为阐明AM基因表达的调控机制，利用荧光素酶载体，在体外培养的人主动脉内皮细胞（HAEC）中检测AM基因5 '侧翼区的功能元件。AM基因5 ′侧翼DNA启动子活性降低，缺失-85 ~-93 bp的NF-IL 6位点、-33 ~-68 bp的AP-2位点和-21 ~-26 bp的TATA盒。这些顺式作用元件可能参与了EC中人AM基因的转录调控，但AM诱导的血管舒张是否具有内皮依赖性尚不清楚。内皮剥脱可抑制AM对主动脉环的舒张反应。此外，用cGMP特异性磷酸二酯酶抑制剂E-4021预处理大鼠主动脉环和离体肾脏，可显著增强AM诱导的血管舒张反应，提示NO-cGMP在AM的血管作用中起重要作用。是一种由AM前体加工而成的强效解旋肽。我们已经鉴定出PAMP-12（PAMP[9-20]）猪肾上腺髓质是AM前体的主要产物，并证明其表现出有效的扩张作用。尽管PAMP是否存在特异性受体尚不清楚，但PAMP-12可能与PAMP-20具有共同生物学功能

Adrenomedulin (AM) is a potent vasorelaxant peptide recently isolated from human pheochromocytoma tissue, and is structurally a member of CGRP family. mRNA of AM is highly expressed in several tissues including heart, lung, kindey and vascular wall as well as adrenal medulla. In this project, we have studied the expression and secretion of AM and its signal transduction.To investigate the sites of production and secretion of AM in heart failure, we measured plasma adrenomedullin levels and peptide and mRNA levels of adrenomedullin in various tissues in rats with heart failure. We also examined whether the heart actually secretes AM into the circulation in patients with heart failure. Plasma AM levels were increased in heart failure rats, correlating with ventricular weight. Tissue AM peptide and mRNA levels were increased in the heart and lungs, but not kidney or adrenals of rats with heart failure. Plasma AM levels were higher in the coronary sinus than in the aorta in patients with h … More eart failure. These results suggest that plasma adrenomedullin levels are increased in heart failure in proportion to its severity and that cardiac production and secretion of adrenomedullin is increased in heart failure rats. Lungs may be another site for increased production of adrenomedullin in heart failure rats.To elucidate the regulatory mechanism of human AM gene expression, functional elements of 5'-flanking region of AM gene were examined in cultured human aortic endothelial cells (HAEC) by using a luciferase vector. The promoter activity of AM gene 5'-flanking DNA was reduced by losing NF-IL6 site at -85 to -93 bp, AP-2 sites at -33 to -68 bp and TATA box at -21 to -26 bp. These cis-acting elements are supposed to participate in the transcriptional regulation of human AM gene in ECIt is still unclear whether AM-induced vasodilation is endothelium-dependent. Endothelium-denudation of the aortic ring suppressed the dilatory response to AM.Furthermore, pretreatments of the rat aortic rings and isolated kidney with E-4021, a cGMP specific phosphodiesterase inhibitor, significantly enhanced AM-induced vasodilation, suggesting an important role of NO-cGMP in the vascular action of AM.Proadrenomedullin N-terminal 20 peptide (PAMP-20) is a potent hypotensive peptide processed from the AM precursor. We have identified PAMP-12 (PAMP[9-20]) porcine adrenal medulla as a major product of the AM precursor, and demonstrated that it exhibits a potent hypotensive action. Although the existence of a specific receptors for PAMP remains obscure, PAMP-12 might share a biological functin with PAMP-20 Less