应激性高血压犬鼠脑干及下丘脑-垂体-肾上腺轴中肾上腺髓质素及其受体mRNA表达的改变

采用逆转录- 聚合酶链式反应检测了慢性足底电击结合噪声应激致高血压大鼠下丘脑、延髓、中脑、垂体和肾上腺等组织中编码肾上腺髓质素的肾上腺髓质素前肽原(preproadrenomedullin, ppADM) 基因以及ADM 的特异性受体组件降钙素受体样受体(calcitonin-receptor-like receptor,CRLR)和受体活性调节蛋白2 和3(receptor-activity-modifying proteins, RAMP2 和RAMP3)表达的变化。我们观察到:与对照组相比,以 3- 磷酸甘油醛脱氢酶作为内参照,15 d 足底电击结合噪声应激引起下丘脑、垂体和肾上腺中ppADM mRNA表达上调,而在延髓和中脑表达明显下调(P<0.01 或 P<0.05); CRLR基因表达量正常时在下丘脑相对较高,应激15 d 后CRLR 表达在延髓、中脑和下丘脑下调(P<0.01 或 P<0.05), 而在垂体和肾上腺的表达无明显变化;应激后RAMP2 基因在延髓和下丘脑表达上调,而在肾上腺表达显著下调(P <0.01), 其他部位无明显变化;RAMP3 基因在对照组大鼠的中脑和下丘脑表达较高,在应激性高血压大鼠的下丘脑和垂体表达上调(P<0.01 或P<0.05), 而在中脑和肾上腺表达下调(P<0.05), 在延髓中的表达变化无统计学差异。上述结果提示:慢性足底电击结合噪声应激引起明显的中枢和下丘脑- 垂体-肾上腺轴ADM 及其受体组件CRLR/RAMP2 或CRLR/R     

慢性低氧性肺动脉高压大鼠肺组织肾上腺髓质素-2的变化

目的：研究新的小分子生物活性肽肾上腺髓质素-2（ADM2／IMD）及其受体在慢性低氧性肺动脉高压大鼠肺组织中的变化和可能的作用。方法：SD大鼠随机分成2组（n=10）：正常对照（NC）组和低氧四周（4H）组;放射免疫法测定血浆和肺组织ADM2／IMD和肾上腺素髓质素（ADM）蛋白水平;逆转录-多聚酶链反应（RT-PCR）法测定肺组织ADM2／IMD、ADM及其受体（CRLR,RAMP1,2,3）mRNA表达;免疫组化法测定ADM2／IMD在肺细小动脉的定位表达：结果：①4H组平均肺动脉压（mPAP）、右心室与左心室加室间隔重量比[RV／（LV＋S）]高于NC组（P均〈0．01）。②4H组血浆和肺组织匀浆ADM水平分别为NC组的2．3倍和3．2倍（P均〈0．01）,ADM2／IMD水平分别比NC组高89．6％和45．0％（P分别〈0．01、〈0．05）。③4H组肺组织ADM2／IMD与ADMmRNA表达高于NC组（P分别〈0．01、〈0．05）,CRLR和RAMP1mRNA表达显著低于NC组（P均〈0．01）,而RAMP2和RAMP3mRNA表达水平两组间差异无显著性。①ADM2／IMD主要在大鼠肺细小动脉内皮细胞及血管外膜表达。结论：ADM2／IMD与ADM相似,与大鼠慢性低氧性肺动脉高压病理过程密切相关;ADM2／IMD及其受体CRLR／RAMP1基因表达和／或蛋白合成、代谢的改变可能参与了大鼠慢性低氧性肺动脉高压的发生发展.     

Intermedin/adrenomedullin 2及其受体在慢性低氧性肺动脉高压大鼠右心室的表达变化

本研究探讨了新发现的小分子生物活性肽intermedin／adrenomedullin 2（IMD／ADM2）及其受体在慢性低氧性肺动脉高压大鼠右心室中的变化和可能作用。用放射免疫分析法测定正常对照组和常压低氧4周组Sprague-Dawley大鼠血浆、右心室匀浆IMD／ADM2和肾上腺髓质素（adrenomednllin,ADM）蛋白水平;逆转录-多聚酶链反应法测定右心室IMD／ADM2、ADM及受体：降钙素受体样受体（calcitonin receptor-like receptor,CRLR）、受体活性修饰蛋白1,2,3（receptor activity modifying protein 1,2,3,RAMP1,RAMP2,RAMP3）mRNA表达。结果显示：低氧组平均肺动脉压、右心室与左心室加室间隔重量比[RV／（LV＋S）]显著高于对照组（均P〈0．01）;低氧组血浆和右心室组织匀浆ADM水平比对照组分别高1．26倍和1．68倍（P〈0．01）,IMD／ADM2水平则较对照组分别高0．90倍和1．19倍（P〈0．01）;与对照组相比,低氧组右心室IMD／ADM2、ADM mRNA表达均上调（P〈0．01）,RAMP2 mRNA表达增强（P〈0．05）,而两组间CRLR、RAMP1、RAMP3 mRNA的表达水平无显著性差异。结果表明,慢性低氧性肺动脉高压大鼠IMD／ADM2表达水平升高。     

肾上腺髓质素和降钙素基因相关肽受体在血管平滑肌细胞的脱敏—受体活性修饰蛋白的作用

新近研究发现,肾上腺髓质素（adrenomedullin,ADM)和降钙素基因相关肽（calcitonin gene-related peptide,CGRP)均能与降钙素受体样受体（calcitoni receptor-like receptor,CRLR)结合,其配体特异性由受体活性修饰蛋白（receptor activity-modifying protein RAMP)调控,本工作在离体培养的大鼠胸主动脉血管平滑肌细胞（vsacular smooth muscle cells,VSMCs)上观察ADM和CGRP受体脱敏现象,以探讨CRLR／RAMP假说在心血管组织方面的意义,用无血清培养基（serum-free medium,SFM)和含有10^-8mol/L ADM,CGRP和肾上腺髓素质前体原N－末端20肽（proadrenomedullin N-terminal 20 peptide PAMP）的SFM培养,再用10^-8mol/L ADM或 CGRP和磷酸二酯酶的抑制剂异丙基次黄苷（isobutyryl methyxanthine,IBMX)与VSMCs进行第二次孵育,然后收集细胞,测定VSMCs cAMP含量。10^-8mol/LADM,CGRP和PAMP单独与VSMCs孵育,VSMCs cAMP含量分别较SFM组高191％（P＜0．01）,385％（P＜0．01）和67％（P＜0．05）,预先用10^-8mol/L ADM ak CGRP与VSMCs孵育可降低随后的CGRP刺激VSMCs产生cAMP,分别较单次CGRP育少44％（P＜0．05）和48％（P＜0．01）,预先用100nmol/L蛋白激酶A（PKA）抑制剂H－89处理VSMCs,可完全阻断ADM和CGRP预处理诱导的第二次CGRP刺激的VSMCs cAMP含量减少,表明VSMCs对CGRP的脱敏过程是通过PKA途径实现的,预先用ADM,CGRP处理VSMCs后,用ADM第二次孵育,细胞内cAMP含量与单次ADM孵育无明显改变,PKA抑制H－89与VSMCs孵育,无论对欠ADM刺激或对ADM和CGRP处理的第二次刺激的cAMP生成均无影响,用PAMP处理VSMCs后,ADM和CGRP的第二次刺激的VSMCs cAMP水平无明显改变（P＞0．05）。结果提示,在离体培养的大鼠VSMCs,ADM epc wsg i euk txgtdmj CGRP受体对预先用ADM和CGRP处理后的激动剂的第二次刺激都脱敏,表明ADM和CGRP的脱敏现象不一致。     

左旋硝基精氨酸诱导的高血压大鼠心肌和血管的肾上腺髓质素与受体活性修饰蛋白2表达的变化

探讨高血压大鼠心肌和血管的肾上腺髓质素（adrenomedullin,ADM）与受体活性修饰蛋白2（receptoractivity-modifying protein 2,RAMP2）mRNA的变化。用一氧化氮合酶（NOS）竞争性抑制剂左旋硝基精氨酸（L-NNA）阻断NOS制备大鼠高血压模型。用放射免疫分析方法测定血浆、心肌和血管ADM含量,及竞争性定量RT-PCR方法测定心肌和血管ADM mRNA与RAMP2 mRNA含量。结果表明,NOS阻断剂L-NNA应用4周后动物血压明显升高、心肌肥厚。心重（mg）/体重（g）比值增加35.5％（P<0.01）。血浆、心肌和血管的ADM-ir较对照组分别增加80％、72％和57％（均P<0.01）。高血压大鼠心肌和血管ADM mRNA含量显著增加,分别较正常大鼠高50％（P<0.05）和102.9％（P<0.05）。高血压大鼠心肌和血管的RAMP2　mRNA含量均显著增加,分别较正常大鼠高132％（P<0.01）和87％（P<0.01）。高血压大鼠心肌和血管ADM的升高与RAMP2的升高程度呈明显的正相关,其相关系数分别为0.741和0.885。上述观察结果表明,高血压时血浆、心肌和血管ADM水平升高,心肌和血管ADM与RAMP2基因表达上调,提示ADM/RAMP2系统在高血压发病中可能具有重要作用。     

淫羊藿总黄酮对肾阳虚大鼠下丘脑-垂体-肾上腺轴钙调蛋白基因表达的影响

目的:从分子水平探讨肾阳虚证病理改变及淫羊藿总黄酮的作用及其机理,为开发药物的临床新用途提供理论依据.方法:用大剂量外源糖皮质激素建立肾阳虚大鼠动物模型,以实时荧光定量RT-PCR技术,测定各组大鼠下丘脑-垂体-肾上腺轴CaM mRNA的表达,以及淫羊藿总黄酮对其的影响.结果:肾阳虚大鼠下丘脑、肾上腺CaMmRNA水平升高,垂体组织CaM mRNA水平没有显著变化,淫羊藿总黄酮能够降低下丘脑组织CaM mRNA水平,但对肾上腺影响不显著.结论:大鼠肾阳虚证时下丘脑中CaM mRNA水平升高,淫羊藿总黄酮可使其降低.     

大鼠慢性多重应激模型的建立

目的:建立大鼠慢性多重应激模型,为研究应激性疾病提供实验模型.方法:健康雄性SD大鼠随机分为模型组(n=10)和对照组(n=10).模型组采用脉冲随机变动的噪声、夜间光照、足底电击以及强迫游泳和束缚的复合刺激为应激源,对大鼠实施刺激,观察行为变化,检测心率、血压、体重增长速率、食物利用率,测定血清ACTH和皮质酮并进行分析.结果:慢性多重应激大鼠由实验之初的兴奋状态逐渐进入抑制状态,血压心率上升,体重增长缓慢,食物利用率降低,血清ACTH和皮质酮增高.结论:慢性多重应激大鼠一般行为、基本生理体征和下丘脑-垂体-肾上腺轴(HPA)功能发生改变,应激反应处于持续亢奋状态,该模型是较稳定较理想的应激模型.     

应激引起血压升高大鼠血管升压素V1受体mRNA水平改变

实验在雄性ＳｐｒａｇｕｅＤａｗｌｅｙ 大鼠上进行。实验动物被随机分为对照组和应激组, 应激组大鼠每天给予电击足底结合噪声的应激刺激, 每日２ 次, 每次２ ｈ 。应激组大鼠在接受连续１５ ｄ 的慢性应激刺激后, 其尾动脉收缩压与对照动物相比有显著升高。对照组为１６－２５ ±０－６３ｋＰａ （ｎ ＝ ７） ; 应激组为１９－５５ ±１－４５ ｋＰａ （ｎ ＝ ８, Ｐ＜ ０－０５） 。用ＲＴＰＣＲ 结合Ｓｏｕｔｈｅｒｎ 印迹核酸分子杂交技术观察到, 血管升压素（ｖａｓｏｐｒｅｓｓｉｎ, ＡＶＰ）Ｖ１ 受体ｍＲＮＡ 广泛存在于大鼠下丘脑、皮质、延髓等部位以及心脏、肝脏、肾脏等组织中。用定量ＰＣＲ 方法观察到, 大鼠在接受慢性应激刺激之后, 其大脑顶叶皮质、下丘脑及延髓组织中ＡＶＰＶ１ 受体ｍＲＮＡ 水平均显著低于正常大鼠（ 顶叶皮质： Ｐ＜ ０－０５ ; 下丘脑： Ｐ＜ ０－０１ ; 延髓： Ｐ＜ ０－００１） , 而心脏、肝脏及肾脏组织中的ＡＶＰＶ１ 受体ｍＲＮＡ水平与正常大鼠相比均无明显差别（ 心脏： Ｐ＞ ０－０５ ; 肝脏： Ｐ＞ ０－０５ ; 肾脏：Ｐ＞ ０－０５） 。上述结果提示, 慢性应激刺激可引起大鼠不同部位脑组织ＡＶＰＶ１ 受体合成水平下调, 可能导致     

肾上腺髓质素调节诱导型一氧化氮合酶对缺氧肺动脉平滑肌细胞增殖和凋亡的影响

目的:探讨缺氧对肺动脉平滑肌细胞(PASMC)增殖和凋亡的影响以及诱导型一氧化氮合酶(iNOS)的蛋白表达变化及肾上腺髓质素(ADM)在缺氧影响PASMC增殖和凋亡中的作用与意义.方法:离体缺氧培养大鼠PASMC,采用MTT比色法和PCNA的免疫组化法测定细胞增殖反应,采用流式细胞仪法检测细胞凋亡情况,采用Westen blot蛋白印迹法检测iNOS的蛋白表达.结果:①MTT法发现,缺氧24 h组的A值明显高于常氧组(P＜0.01),而缺氧 ADM组明显低于缺氧组(P＜0.01),与常氧组比较差别无显著性(P＞0.05),缺氧 L-NAME组A值明显高于缺氧组和常氧组(P＜0.01).②免疫组化法发现,常氧组PCNA呈弱阳性表达,而缺氧24 h组PCNA呈阳性表达(P＜0.01).ADM明显抑制了缺氧24 h组PCNA的表达(P＜0.01);而L-NAME则促进了缺氧24 h组PCNA的表达(P＜0.01).③流式细胞仪分析发现,常氧组、缺氧组、缺氧 ADM组、缺氧 L-NAME组,在缺氧培养24 h后,其凋亡指数比较差别无显著性(P均＞0.05).④Westen blot发现常氧组大鼠PASMC见少量iNOS表达,缺氧4 h后,表达明显增多(P＜0.01),8h,24 h持续高表达(P＜0.01);L-NAME对iNOS蛋白的表达没有影响.ADM促进iNOS蛋白的表达.结论:①缺氧能促进肺动脉平滑肌细胞低氧性增殖,对肺动脉平滑肌细胞的凋亡无影响.②缺氧能诱导肺动脉平滑肌细胞表达iNOS,ADM能促进iNOS的表达,ADM、iNOS在HPH发展中可能起到抑制作用.     

重复制动应激对雌性大鼠下丘脑-垂体-卵巢轴的影响

目的: 探索重复制动应激对雌性大鼠下丘脑-垂体-卵巢轴的影响。方法: 40只SD雌鼠随机分为两组(n=20),对照组和实验组,一组正常饲养,一组采取递增负荷束缚应激,每天置于束缚器内制动应激一次(从上午9:00开始),第1日制动2 h,以后采用递增负荷,每日增加0.5 h,持续两周,通过检测体重、脏器系数、动情周期、性激素、病理和相关基因的表达探索其对下丘脑-垂体-卵巢轴的危害。结果: 重复制动应激使雌性大鼠体重下降、动情周期延长,卵巢和子宫的脏器系数和形态发生改变,利用qPCR技术对其相关基因检测,发现下丘脑促性腺激素释放激素、垂体促性腺激素释放激素受体、促卵泡生成素和促黄体生成素mRNA的表达显著下降,卵巢促卵泡生成素和黄体生成素受体 mRNA的表达显著上升,卵巢和子宫雌激素受体mRNA的表达显著下降。结论: 重复制动应激可能通过干扰下丘脑-垂体-卵巢轴的内分泌调节作用,使动情周期紊乱,从而损伤雌性动物的性腺和生殖内分泌功能。     

The role of adrenomedullin and its receptor system in cardiovascular calcification of rat induced by Vitamin D(3) plus nicotine

Adrenomedullin (ADM) is a potent vasodilatory peptide which regulates blood pressure, cell growth and bone formation. Our work was aimed to explore the production of ADM, changes and pathophysiological significance of ADM mRNA and ADM receptor components--calcitonin receptor like receptor (CRLR) and receptor activity modifying proteins (RAMPs) mRNA in calcified myocardium and aorta of rats induced by Vitamin D3 plus nicotine. Contents of ADM in plasma, myocardium and aorta were measured by radioimmunoassay (RIA). The amount of ADM, CRLR and RAMPs mRNA was determined by semi-quantitative RT-PCR. The calcium content and alkaline phosphatase activity in myocardium and aorta of rats were measured. The results showed that the contents of calcium in calcified myocardium and aorta were increased by 3.5- and 6-fold (all P < 0.01), respectively, and alkaline phosphatases activity in calcified myocardium and aorta were increased by 66.5 and 82.7% (all P < 0.01 ), respectively, compared with control. Contents of ADM in plasma, myocardium and aorta were increased by 58% (P < 0.01), 14.3% (P < 0.01) and 27.8% P < 0.05). Furthermore, it was found that the amount of ADM, CRLR and RAMP2 mRNA in calcified myocardium was elevated by 90.6, 157.5 and 119.6% (all P < 0.01), RAMP3 mRNA was decreased by 14.1% (P < 0.01), respectively, compared with control. The amount of ADM, CRLR, RAMP2 and RAMP3 mRNA in calcified aorta was elevated by 37.7% (P < 0.01), 41.4% (P < 0.01), 60.1% (P < 0.05) and 13% P < 0.01), respectively, compared with control. The elevated level of CRLR and RAMP2 mRNA were in positive correlation with that of ADM mRNA (r = 0.992 and 0.882, respectively, P < 0.01) in calcified myocardium. The elevated level of CRLR and RAMP3 mRNA were also in positive correlation with that of ADM mRNA (r = 0.727, P < 0.05 and 0.816, P < 0.01, respectively) in calcified aorta. These results demonstrated that calcified myocardium and aorta generated an increased amount of ADM, up-regulated gene expressions of ADM, CRLR and RAMP2 mRNA. While the alteration of RAMP3 mRNA in calcified myocardium and aorta was different. These suggested that ADM and its receptor system might involve in the regulation of calcification in heart and aorta.     

Increased myocardial expression of RAMP1 and RAMP3 in rats with chronic heart failure

Calcitonin gene-related peptide (CGRP) and adrenomedullin (ADM) are potent vasodilators in humans and improved myocardial ischemia is observed after CGRP administration. Receptors for CGRP and ADM were already identified in heart. Receptor activity-modifying proteins (RAMPs) determine the ligand specificity of the calcitonin receptor-like receptor (CRLR); co-expression of RAMP1 and CRLR results in a CGRP receptor, whereas the association of RAMP2 or RAMP3 with CRLR gives an ADM receptor. As CGRP and ADM may play a beneficial role in heart failure, we investigated whether the CGRP and ADM receptors are upregulated in chronic heart failure. We have used semi-quantitative RT-PCR and Western-blot analysis to detect and quantify the mRNA and the protein of RAMP1 and RAMP3 in both atria and ventricles of failing hearts 6 months after aortic banding in rats. Our results showed for the first time an up-regulation of RAMP1 and RAMP3 mRNAs and proteins in this model of cardiac failure. No change was observed in mRNAs coding for CRLR, RAMP2, RDC1 (canine orphan receptor), and ADM. The present results suggested after congestive heart failure in adult rats, an up-regulation of the CGRP receptor (by an increase in RAMP1 that is associated with CRLR) in atria and ventricles and of ADM receptor (by increased RAMP3 expression that is associated with CRLR) in atria. These findings support a functional role for CGRP and ADM receptors to compensate the chronic heart failure in rats.     

Alterations of adrenomedullin and its receptor system components in calcified vascular smooth muscle cells

Vascular calcification is a common finding in many cardiovascular diseases. Paracrine/autocrine changes in calcified vessels, and the secreted factors participate in and play an important role in the progress of calcification. Adrenomedullin (ADM) is a potent vasodilator peptide secreted by vascular smooth muscle cells (VSMCs) and vascular endothelial cells. Recently, receptor activity-modifying proteins (RAMPs) have been shown to transport calcitonin receptor-like receptor (CRLR) to the cell surface to present either as CGRP receptor or ADM receptor. In this work, we explored the production of ADM, alterations and significance of ADM mRNA and its receptor system components—CRLR and RAMPs mRNA in calcified VSMCs. Our results showed that calcium content, ⁴⁵Ca²⁺ uptake and alkaline phosphatases (ALPs) activity in calcified VSMCs were increased, respectively, compared with control VSMCs. Content of ADM in medium was increased by 99% (p<0.01). Furthermore, it was found that the levels of ADM, CRLR, RAMP2 and RAMP3 mRNA in calcified cells were elevated, respectively, compared with that of control. The elevated levels of CRLR, RAMP2 and RAMP3 mRNA were significant correlation with ADM mRNA (r=0.83, 0.92 and 0.93, respectively, all p's<0.01) in calcified VSMCs. The results show that calcified VSMCs generate an increased amount of ADM, up-regulate gene expressions of ADM and its receptor system components—CRLR, RAMP2 and RAMP3, suggesting an important role of ADM and its receptor system in the regulation of vascular calcification.     

mRNA expression of novel CGRP1 receptors and their activity-modifying proteins in hypoxic rat lung

Calcitonin gene-related peptide (CGRP) is a potent vasodilator. Our group has reported that exogenous CGRP may prevent or reverse hypoxic pulmonary hypertension in rats. The vasodilatory action of CGRP is mediated primarily by CGRP1 receptors. The calcitonin receptor-like receptor (CRLR) and the orphan receptor RDC-1 have been proposed as CGRP1 receptors, and recent evidence suggests that CRLR can function as either a CGRP1 receptor or an adrenomedullin (ADM) receptor. Receptor activity-modifying proteins (RAMPs) determine the ligand specificity of CRLR: coexpression of CRLR and RAMP1 results in a CGRP1 receptor, whereas coexpression of CRLR and RAMP2 or -3 results in an ADM receptor. We used qualitative, semiquantitative, and real-time quantitative RT-PCR to detect and quantitate the relative expression of these agents in the lungs of rats exposed to normoxia (n = 3) and 1 and 2 wk of chronic hypobaric hypoxia (barometric pressure 380 mmHg, equivalent to an inspired O(2) level of 10%; n = 3/time period). Our results show upregulation of RDC-1, RAMP1, and RAMP3 mRNAs in hypoxic rat lung and no change in CRLR and RAMP2 mRNAs. These findings support a functional role for CGRP and ADM receptors in regulating the adult pulmonary circulation.     

RAMPs and CRLR expressions in osteoblastic cells after dexamethasone treatment

Adrenomedullin (ADM) is a potent stimulator of osteoblastic activity and promotes bone growth in vivo. ADM receptors are formed by heterodimerization of the CRLR and a RAMP2 or RAMP3 molecule. Since glucocorticoid responsive elements were recently identified in the human CRLR promoter and that glucocorticoids exert a major action in bones, we investigated the acute effect of dexamethasone (Dex) treatment on ADM receptor components in osteoblastic cell types: the MC3T3-E1 cells and calvaria-derived osteoblastic cells. Changes in expression of CRLR and RAMPs molecules were evaluated at mRNA levels using RT-PCR and at protein levels by Western blot analysis. We found that Dex increased expression of RAMP1 and RAMP2 mRNA in a time-dependent but dose-independent manner, while RAMP3 was unchanged. In contrast, Dex decreased the CRLR mRNA expression and these changes were reflected at protein levels. We suggest that Dex, in osteoblastic cells, altered ADM receptor by inhibition of CRLR expression and consequently could impair the ADM anabolic effect on bone. Our findings could explain in part, the detrimental side effects observed at bone level during glucocorticoid therapy.     

Changes of adrenomedullin and receptor activity modifying protein 2 (RAMP2) in myocardium and aorta in rats with isoproterenol-induced myocardial ischemia

Adrenomedullin is a potent vasodilator peptide originally isolated from a pheochromocytoma. Recently, a novel adrenomedullin receptor has been identified as a complex of calcitonin receptor-like receptor (CRLR) and receptor activity modifying protein 2 (RAMP2). To explore the pathophysiological roles of adrenomedullin and its receptor component RAMP2 in ischemic cardiovascular diseases, we studied the changes of adrenomedullin and RAMP2 mRNA in myocardium and aorta in rats with isoproterenol (ISO)-induced myocardial impairment. In ISO-treated rats, heart became enlarged markedly, the ratio of heart to body weight was increased by 54% (P<0.01), and myocardial malondialdehyde content and plasma lactate dehydrogenase activity was elevated by 43% (P<0.01) and 138% (P<0.01), respectively. Immunoreactive adrenomedullin (ADM) in plasma, myocardium and aorta was augmented by 116.7% (P<0.01), 50.8% (P<0.01) and 12.5% (P>0.05), respectively. ADM mRNA in myocardium and aorta was increased by 96.8% (P<0.01) and 38.5% (P<0.01), respectively. RAMP2 mRNA in myocardium and aorta was increased by 19.6% (P<0.05) and 15.8% (P<0.01), respectively. These results suggest that the increase of ADM level and the up-regulation of ADM and RAMP2 gene in myocardium and aorta may be significant in the pathogenesis of ischemic myocardiopathy.     

Autonomic and neuroendocrine actions of adrenomedullin in the brain: mechanisms for homeostasis

In addition to its role as a potent vasodilator, adrenomedullin (ADM) affects an animal's physiological status through its effects in the brain. We have shown that circulating ADM activates neurons, including nitric oxide (NO)-producing neurons, in autonomic centers of the brain such as the hypothalamic paraventricular nucleus (PVN). Systemic ADM gains access to the brain through the area postrema (AP), a brainstem circumventricular organ, and the PVN is a major target of these ADM-sensitive AP neurons. Neurons expressing the preproADM (ppADM) gene are distributed throughout the brain, with high levels in autonomic centers. Lipopolysaccharide (LPS, immune stress), restraint (psychological stress), and 24 h dehydration all down-regulate ppADM gene expression in different subsets of autonomic centers. Receptor-activity-modifying protein (RAMP) 2 and RAMP3, ADM receptor subunits, are expressed in autonomic centers including the PVN and supraoptic nucleus. Intracerebroventricular injections of ADM increase arterial pressure, heart rate, tyrosine hydroxylase mRNA levels in the locus coeruleus, plasma levels of ACTH, and NO production in the hypothalamus. ADM excites putative GABAergic and cholinergic neurons in dissociated cells from a basal forebrain integrative center, the diagonal band of Broca. These results demonstrate that the signalling components necessary for ADM to influence physiological systems are present in the brain and that ADM is an important transmitter of brain autonomic pathways which are involved in regulating homeostatic balance.