Human B-type natriuretic peptide is not degraded by meprin A

B-type natriuretic peptide (BNP) combats cardiac stress by reducing blood pressure and ventricular fibrosis. Human BNP is inactivated by unknown cell surface proteases. N-terminal cleavage of mouse BNP by the renal protease meprin A was reported to increase inactivating degradation by a second protease named neprilysin. Since the sequence surrounding the meprin A cleavage site in BNP differs between species, we tested whether meprin A degrades human BNP. Using a recently developed proteolytic bioassay, the ability of various protease inhibitors to block the inactivation of BNP was measured. In rat kidney membranes, inhibitors of meprin A or neprilysin partially or completely blocked inactivation of rat BNP_1-32 when added individually or in combination, respectively. In contrast, neither inhibitor alone or in combination prevented the inactivation of human BNP_1-32 by human kidney membranes. Leupeptin, a serine protease inhibitor, totally blocked inactivation of human BNP by human membranes, substantially blocked the inactivation of rat BNP_1-32 by human membranes, but had no effect on the inactivation of rat BNP_1-32 by rat kidney membranes. Purified neprilysin reduced the bioactivity of rat BNP_1-32 and human BNP. Digestion with both meprin and neprilysis caused the greatest reduction in rat BNP_1-32 but had no effect on the bioactivity of human BNP_1-32. We conclude that meprin A does not degrade BNP in humans and should not be considered a pharmacologic target of the natriuretic peptide system.     

正常成人血浆环核苷酸水平

本文应用~(125)I-cAMP及~(125)I-cGMP放射免疫分析法测定健康成人血浆中环核苷酸的含量。血浆中cAMP含量,男性为24.75±7.41Pmol/ml,女性为23.59±5.71Pmol/ml。cGMP含量,男性为4.04±1.58Pmol/ml,女性为4.88±1.35pmol/ml。cAMP/cGMP含量之比值,男性为6.96±2.58,女性为4.97±1.41。经统计学处理(t检验),男女之间血浆cAMP含量无显著性差异(P>0.05),而cGMP含量及cAMP/cGMP含量之比值有显著性差异(P<0.01),本文认为这可能与女性月经周期内分泌功能改变有关。     

CGMP Levels Following ANF Challenge are Markers of Subsequent Successful Reversion of Lone Atrial Fibrillation to Sinus Rhythm

The aim of the present study was to assess whether cGMP release to ANP stimulation can be a biochemical marker of subsequent successful electrical cardioversion of lone atrial fibrillation to sinus rhythm. For this purpose, we studied 13 patients with chronic, lone atrial fibrillation of less than one year's duration who presented to our laboratory for electrical therapy of their arrhythmia. Prior to electrical cardioversion, peripheral venous cGMP levels were assessed at baseline and following an tntravenous challenge of 50 Ug human ANP. Venous blood samples for cGMP assessment were taken a) at baseline, b) 5 and 10 mins after the end of ANP infusion. ANOVA of repeated measures was used for statistical analysis. Eight of the study patients were successfully cardioverted to sinus rhythm, while the remaining 5 were not. Although no difference was noted between the two groups regarding the mean time of arrhythmia duration as well as left atrial and ventricular dimensions, ANP stimulation provoked significantly greater cGMP release in patients whose arrhythmia reverted to sinus rhythm, when compared with that of patients whose arrhythmia persisted (p<0.001). Therefore, cGMP levels following ANP challenge might discriminate between patients with chronic AF who are going to be successfully cardioverted and those who are not. These findings imply that the underlying atrial disease might be different in extent/nature between patients with lone AF responsive to cardioversion and those with resistant arrhythmia.     

cGMP信号传导通路及钙敏感钾通道在D型钠尿肽抑制豚鼠胃动力中的作用

目的观察豚鼠胃内是否存在钠尿肽（NP）受体,并观察cGMP信号传导通路及钙敏感钾通道在D型钠尿肽（DNP）抑制豚鼠胃动力中的作用。方法用放射自显影技术检测NP受体在胃内的分布,用四道生理记录仪记录胃平滑肌的自发性收缩活动,用膜片钳技术的全细胞技术记录钙敏感钾电流。结果 NP受体存在于豚鼠胃底、胃体和胃窦,并在胃窦部密度最大。DNP抑制胃窦环形肌自发性收缩活动并呈现剂量依赖关系,DNP的这种抑制效应被鸟苷酸环化酶抑制剂LY83583所减弱而被cGMP敏感的磷酸酯酶抑制剂所增强。非选择性钾通道抑制剂四乙胺明显抑制DNP对豚鼠胃窦环形肌自发性收缩活动的抑制作用。10 nmol/L的DNP增加豚鼠胃窦环形肌上钙敏感钾通道。结论 NP受体存在于豚鼠胃内并在胃窦部位分布密度最大,DNP明显抑制豚鼠胃窦环形肌自发性收缩活动,这种抑制效应可能通过cGMP途径实现,并且钙敏感钾通道可能也参与此过程。     

Identification of a possible role for atrial natriuretic peptide in MDMA-induced hyperthermia

MDMA (3,4-methylenedioxymethamphetamine) induces thermogenesis in a mitochondrial uncoupling protein 3-dependent manner. There is evidence that this hyperthermia is mediated in part by the lipolytic release of free fatty acids, that subsequently activate uncoupling protein 3 in skeletal muscle mitochondria. We hypothesize that atrial natriuretic peptide (ANP), a strong lipolytic mediator, may contribute to the induction and maintenance of MDMA-induced thermogenesis. The specific aims of this study were to (1) determine if ANP is released following MDMA administration, and (2) use the ANP receptor antagonist, Anantin, to ascertain the role of ANP in MDMA-induced hyperthermia. ANP levels were measured in plasma at baseline, 10, 20, 30 and 60 min following MDMA (40 mg/kg, sc) administration in 16 male Sprague-Dawley rats. A robust increase in ANP was seen within 10 min of MDMA administration. ANP levels returned to baseline at 20 min and then gradually rose over the 60 min monitoring period. The administration of Anantin (40 mg, ip), 15 min before and after MDMA, significantly attenuated the MDMA-induced hyperthermia. We conclude that ANP signaling contributes to the hyperthermia induced by MDMA.     

六味地黄汤醇提水洗脱部位对小鼠阴虚模型的影响

目的观察六味地黄汤醇提水洗脱部位对阴虚小鼠体质量、免疫功能、肝组织氧化指标和cAMP、cGMP、T3、T4含量的影响,评价其滋阴作用。方法将小鼠每日灌胃给予甲状腺片(150 mg·kg-1)和利血平(1 mg·kg-1)致阴虚模型,同时给予治疗药物,7 d后检测小鼠体质量增长率、胸腺、脾指数及血浆中cAMP、cGMP、T3、T4,肝匀浆SOD、GSH-Px和MDA等,观察六味地黄汤醇提水洗脱部位对阴虚型小鼠的影响。结果六味地黄汤醇提水洗脱部位能提高阴虚小鼠体质量增长率、胸腺和脾脏指数,降低阴虚小鼠肝组织中SOD和GSH-Px活性,升高MDA含量,降低血清cAMP、T3、T4含量和cAMP/cGMP比值,高剂量组与模型组比较有统计学意义(P<0.05,P<0.01);六味地黄汤亦可改善以上各项指标,但与模型组相比无统计学意义。结论六味地黄汤醇提水洗脱部位具有显著滋阴作用,优于传统六味地黄汤煎剂。     

论FDA的cGMP现场检查域外效力

目的 从法理和实践两个方面,论述FDA cGMP现场检查的域外效力.方法 介绍了FDA现场检查的演变脉络和FDA cGMP现场检查域外效力的发展情况以及推行手段,初步提出我们的应对策略.结果 为了保护本国公民的健康,FDA对药品监管从国内检查扩展到国外cGMP现场检查.虽然FDA的cGMP现场检查域外效力会带来主权和法律等方面的一些冲突,但重要的是,它借助双边协作与多边论坛等载体,从冲突走向融合,实现了双惠与多惠.结论 FDA的cGMP现场检查域外效力的启示在于,采取开放、融合的态度是我们应对FDA的cGMP现场检查域外效力的较佳策略,SFDA应积极行政以担当起保障我国公众健康之职责.     

平喘宁对哮喘大鼠肺组织cAMP/cGMP及TGF-β1 mRNA表达的影响

目的:研究平喘宁对寒性哮喘大鼠肺组织中cAMP/cGMP及TGF-β1表达水平的影响。方法:雄性Wistar大鼠70只,随机分为空白对照组、模型组、地塞米松组、桂龙咳喘宁组以及平喘宁高、中、低剂量组。以卵蛋白致敏及寒冷刺激复制大鼠哮喘模型,造模7 d后,各治疗组开始给药,空白对照组、模型组每天给予等量蒸馏水灌胃。4 w后取出肺组织,采用ELISA法检测大鼠肺组织cAMP、cGMP含量,并计算cAMP/cGMP;采用逆转录-聚合酶链式反应(RT-PCR)半定量检测TGF-β1 mRNA表达丰度。结果:与模型组比较,平喘宁高、中、低剂量组cGMP含量降低,cAMP/cGMP上升,TGF-β1 mRNA表达水平降低(P<0.01,P<0.05)。结论:平喘宁可明显减轻哮喘大鼠气道炎症反应,逆转气道重构。     

荭草苷对大鼠急性心肌梗死的保护作用及机制研究

目的 探讨荭草苷对急性心肌梗死模型大鼠的保护作用及机制。方法 建立异丙肾上腺素致大鼠急性心肌梗死模型,将大鼠分为正常对照组、模型组、阳性药普萘洛尔组及低、高剂量荭草苷干预组（1.0、2.0 mg/kg）;采用多道生理记录仪采集心电图、血流动力学指标,检测血清中心肌酶、抗氧化物酶的活性,HE染色观察心肌组织病理学改变,ELISA法检测心肌组织环鸟苷酸（cGMP）水平。结果 与模型组比较,预防性ip 2.0 mg/kg荭草苷连续7 d,可降低大鼠心电图ST段高度变化,明显改善大鼠血流动力学指标,降低大鼠血清心肌酶LDH、ALT和AST的水平,减轻心肌梗死大鼠心肌纤维变性坏死及水肿程度,亦可升高大鼠血清中抗氧化酶SOD、GSH-Px活性及心肌组织中cGMP水平。结论 荭草苷对大鼠急性心肌梗死具有明显保护作用,其保护机制可能与增强体内抗氧化酶活性,提高心肌组织cGMP水平和调节NO/cGMP信号通路有关。     

The vasodilator mechanisms of sodium metabisulfite on precontracted isolated aortic rings in rats: Signal transduction pathways and ion channels

Sodium metabisulfite (SMB) is most commonly used as a food additives, however few study was performed on the vasodilator effect of SMB. In the present paper, the vasodilator effects of SMB and roles of Ca²⁺ and K⁺ channels as well as the cGMP pathway on isolated rat aortic rings were studied. The results show that: (1) SMB could relax isolated aortic rings precontracted by norepinephrine in a concentration-dependent manner. The maximal endothelium-dependent vasorelaxation was approximately 20% whereas that not depending on the presence of the endothelium was more than 90%. (2) The vasorelaxant effects induced by 50 or 200 μM SMB were partially inhibited by iberiotoxin, NS-2028 or l-NNA. The vasorelaxation of 1000 μM SMB was partially inhibited by nifedipine or glibenclamide. The SMB induced vasorelaxation was partially inhibited by tetraethylammonium. These results led to the conclusions that the vasorelaxation of SMB at low concentrations (<400 μM) was endothelium-dependent and mediated by the cGMP pathway and BK_Ca channel, but at high concentrations (>500 μM) was endothelium-independent and mediated by K_ATP channel and L-type Ca²⁺ channel. The maximal allowable concentration from China and the acceptable daily intake level from WHO of SMB as a food additive should be revised.