心钠素的生物学效应

心钠素的生物学效应刘桂萍（吉林省白城高等师范专科学校生物系,１３７０００）付晶（吉林省长春市宽城区中医院,１３００５１）心钠素（ＡＮＰ）是８０年代初由加拿大,美国及日本学者先后从人及大鼠的心房肌细胞中分离纯化出的一种循环激素。它具有强大的利钠、利尿、...     

心钠素前体分子内调控对心肌Na^＋—K^＋—ATP酶的作用

目的：研究利钾尿肽及心钠素前体分子内调控作用对心肌Ｎａ＋Ｋ＋ＡＴＰ酶的作用。方法：将大鼠心肌匀浆后,分别加入利钾尿肽、心钠素以及利钾尿肽＋心钠素,用比色法测定Ｎａ＋Ｋ＋ＡＴＰ酶活性。将大鼠心脏悬挂于Ｌａｎｇｅｎｄｏｒｆ灌流装置,分别以利钾尿肽、心钠素、利钾尿肽＋心钠素为灌流液,灌注心脏,用四道生理仪观测左心室内压、左心室收缩最大速率,左心室舒张最大速率,心率及冠脉流量。结果：心钠素虽然对Ｎａ＋Ｋ＋ＡＴＰ酶有抑制作用（抑制率２６．２％）,但是,与对照无显著性差异（Ｐ＞０．０５）。利钾尿肽显著抑制酶的活性（抑制率４６．５％,Ｐ＜０．０１）这种抑制作用可被心钠素抵消（抑制率１７．６％,Ｐ＞０．０５）。利钾尿肽可以增加左心室收缩和舒张最大速率以及左室内压,而这种强心作用可因心钠素的加入而消失或减弱。结论：利钾尿肽可以抑制心肌Ｎａ＋Ｋ＋ＡＴＰ酶的活性,产生强心作用,心钠素可以抵消以上作用。     

心脏分泌的激素—心钠素

心钠素（ＡＮＰ）是由心脏分泌的肽类激素，具有强烈的排钠利尿、降低血压等生理作用。在哺乳动物许多重要器官内均有心钠素的靶组织，心钠素与受体结合后，通过第二信使ｃＧＭＰ发挥生理作用。心钠素的研究具有十分重要的意义。     

人γ心钠素在大肠杆菌中的高效表达

利用聚合酶链式反应（ＰＣＲ）技术扩增人γ心钠素（γ－ｈＡＮＰ）ｃＤＮＡ编码序列,在其５′和３′端分别引入ＥｃｏＲⅠ和ＢａｍＨⅠ限制性内切酶位点,定向克隆到表达质粒载体ｐＭＳ－３１ｂ,在大肠杆菌ｐｏｐ２１３６中高效表达出人γ心钠素融合蛋白,表达产物占菌体总蛋白的３０～４０％。双向免疫扩散法测定证明表达产物与人α心钠素（α－ｈＡＮＰ）抗血清呈阳性反应,纯化的表达产物经复性处理后能引起大鼠胸主动脉条舒张．     

急性缺氧暴露不同时间家兔血浆心钠素,抗利尿激素,醛固…

本实验观察了８０只家兔在急性缺氧６、１２、２４、４８;６０、７１ｈ后肺指数、血浆心钠素（ＡＮＰ）、抗利尿激素（ＡＶＰ）、醛固酮（ＡＬＤ）及尿量的变化。结果表明：在缺氧２４－７２ｈ,肺指数明显升高,尿量减少、缺氧１６ｈ,血浆ＡＮＰ明显升高;而缺氧４８和６０ｈ无ＡＮＰ升高现象。缺氧７２ｈ,血浆ＡＮＦ又明显高于缺氧前水平;血浆ＡＣＰ只在缺氧２４ｈ明显升高;血浆ＡＬＤ未见显著性变化。这些结果提示：在缺氧状     

急性缺氧暴露不同时间家兔血浆心钠素、抗利尿激素、醛固酮的变化

本实验观察了８０只家兔在急性缺氧６、１２、２４、３６、４８、６０、７１ｈ后肺指数、血浆心钠素（ＡＮＰ）、抗利尿激素（ＡＶＰ）、醛固酮（ＡＬＤ）及尿量的变化。结果表明：在缺氧２４－７２ｈ,肺指数明显升高,尿量减少;缺氧１６ｈ,血浆ＡＮＰ明显升高;而缺氧４８和６０ｈ无ＡＮＰ升高现象。缺氧７２ｈ,血浆ＡＮＦ又明显高于缺氧前水平;血浆ＡＶＰ只在缺氧２４ｈ明显升高;血浆ＡＬＤ未见显著性变化。这些结果提示：在缺氧状态下,ＡＮＰ、ＡＶＰ的释放均与缺氧暴露的时间有关。这些激素的平衡失调可能与急性缺氧性肺水肿的发生有关。     

心律失常豚鼠、猕猴心脏心钠素和抗心律失常肽免疫组织化学研究

本文采用免疫组化方法观察高血钾诱发的心律失常豚鼠（２０例）和猕猴（３例）心脏心钠素（ＡＮＰ）和抗心律失常肽（ＡＭ）免疫反应。结果显示：心律失常组豚鼠和猕猴心脏的ＡＮＰ和ＡＡＰ免疫反应比正常组的明显（Ｐ＜０．０５）,心房肌的ＡＮＰ和ＡＡＰ免疫反应比传导系的明显,但心室肌未见棕色反应产物。ＡＮＰ和ＡＡＰ免疫反应在心脏不同部位反应强度不同可能与心脏传出神经和心肌钙通道的分布有关。     

急性热应激小鼠血浆心钠素、血管紧张素及其体液Na+/K+的变化

观察了小鼠在热应激以及热应激恢复期血浆心钠素（ＡＮＰ）,血管紧张素（ＡⅡ）及其体液中Ｎａ＾＋／Ｋ＾＋的变化。结果表明,经热应激后小鼠血浆ＡＮＰ含量无明显变化,ＡＩＩ含量则明显上升,Ｎａ＾＋／Ｋ＾＋明显减少,肺指数也明显升高,而在热应激的恢复期,小鼠血浆ＡＮＰ却极显著上升,为对照组的２５０％,而ＡⅡ却极显著下降,为对照组的４７％,尿Ｎａ＾＋／Ｋ＾＋值仍持续降低,而肺指数却回降么正常水平,这些结果揭示     

不同生理状态对大鼠右心耳肌细胞特殊颗粒的影响──形态学和计量学研究

本文通过电镜观察和立体计量学方法,研究迷走神经和肾上腺素对ＳＤ大鼠右心耳肌细胞特殊颗粒（ＳＧ）的影响。结果是迷走神经切除组ＳＧ的体密度（ＶＶ）、颗粒平均直径（Ｄ）明显小于对照组（Ｐ＜０．００１）,肾上腺素组ＳＧ的ＶＶ、Ｄ、数密度（Ｎｖ）也明显小于相应对照组（Ｐ＜０．００１）。结果提示迷走神经对心钠素的释放是抑制作用,肾上腺素对心钠素的释放是促进作用。本研究还为ＳＧ的产生与分型,心钠素的多种释放方式提供了形态学资料。     

酸枣的组织培养和植株再生

１植物名称酸枣（Ｚｉｚｙｐｈｕｓ　ｊｕｊｕｂａｖａｒ．Ｓｐｉｎｏｓａ）。２材料类别沂河岸堤自然生长的野生植株上的嫩芽。３培养条件诱导愈伤组织培养基：（１）ＭＳ＋６－ＢＡ２ｍｇ·Ｌ’（单位下同）＋ＮＡＡ０．１;（２）ＭＳ＋６－ＢＡ２＋ＮＡＡ０．２;（３）ＭＳ＋６．ＢＡ２＋ＮＡＡ０．４;（４）ＭＳ＋６．ＢＡ２＋ＮＡＡ１;（５）ＭＳ＋６．ＢＡ２＋ＮＡＡ０．０１;（６）ＭＳ＋６．ＢＡ２＋ＮＡＡ０．０５;（７）ＭＳ＋６－ＢＡＩ＋ＮＡＡ０．５。芽分化培养基：（８）ＭＳ＋６－ＢＡＩ;（９）ＭＳ＋６－ＢＡ２;（…     

Guanylyl cyclase / atrial natriuretic peptide receptor-A: role in the pathophysiology of cardiovascular regulation

Atrial natriuretic factor (ANF), also known as atrial natriuretic peptide (ANP), is an endogenous and potent hypotensive hormone that elicits natriuretic, diuretic, vasorelaxant, and anti-proliferative effects, which are important in the control of blood pressure and cardiovascular events. One principal locus involved in the regulatory action of ANP and brain natriuretic peptide (BNP) is guanylyl cyclase / natriuretic peptide receptor-A (GC-A/NPRA). Studies on ANP, BNP, and their receptor, GC-A/NPRA, have greatly increased our knowledge of the control of hypertension and cardiovascular disorders. Cellular, biochemical, and molecular studies have helped to delineate the receptor function and signaling mechanisms of NPRA. Gene-targeted and transgenic mouse models have advanced our understanding of the importance of ANP, BNP, and GC-A/NPRA in disease states at the molecular level. Importantly, ANP and BNP are used as critical markers of cardiac events; however, their therapeutic potentials for the diagnosis and treatment of hypertension, heart failure, and stroke have just begun to be realized. We are now just at the initial stage of molecular therapeutics and pharmacogenomic advancement of the natriuretic peptides. More investigations should be undertaken and ongoing ones be extended in this important field.     

Superactive analogs of the atrial natriuretic peptide (ANP)

Three analogs of the atrial natriuretic peptide ANP(105-126), lacking the N-terminal exocyclic peptide segment and containing 2-mercaptoacetic acid, 3-mercaptopropionic acid or 4-mercaptobutyric acid in place of the cysteine residue in position 105 of the peptide sequence, were synthesized by the solid-phase method. The resulting des-amino analogs showed 2 to 4 times higher diuretic/natriuretic activity than the most active natural ANP and displayed a potent hypotensive effect as well. All three analogs were relatively less potent in various in vitro bioassays and in a binding assay, indicating that their high activities in vivo may be due to resistance to enzymatic degradation and to reduced non-specific tissue adsorption. These compounds not only will serve as useful pharmacologic tools but also represent prototypes for the development of further reduced-size ANP analogs.     

Atriopeptin biochemical pharmacology

Several low-molecular-weight peptides that possess potent natriuretic, diuretic, and vascular smooth muscle relaxant activity have been isolated from atrial extracts. Elucidation of their structure indicates that they consist of a 17-membered ring of amino acids formed by a cystine disulfide bond and that they differ only in the composition of the amino and carboxy termini. The 24-amino-acid peptide atriopeptin (AP) III was selected as the reference compound for structure-activity studies. Amino-terminal amino acid extensions on APIII markedly increase the natriuretic-diuretic but not the renal vasodilatory response in anesthetized dogs, which suggests a heterogeneity of AP receptors in renal tubular and vascular tissues. Radioligand (125I-labeled APIII) binding studies with fresh rat kidney slices indicate that the primary renal sites of specific AP binding are in the glomerulus and in the papillary segment of the medulla, thus implicating these structures in the natriuretic-diuretic effect. Data obtained from radioimmunoassay, chromatographic migration, vasorelaxant biological activity, and peptide sequence analysis indicate that Ser-Leu-Arg-Arg-APIII is the major circulating form of low-molecular-weight atrial peptide present in rat plasma. Circulating APs fulfill many of the criteria for involvement in the endocrine regulation of fluid and electrolyte homeostasis.     

Vasodilatory and diuretic actions of alpha-human atrial natriuretic polypeptide (alpha-hANP)

Vascular and diuretic actions of synthetic alpha-human atrial natriuretic polypeptide (alpha-hANP) were studied using anesthetized dogs and isolated canine arterial strip preparations. alpha-hANP, when given intra-arterially or intravenously, dilated the renal artery more selectively than the vertebral, femoral, common carotid and coronary arteries. alpha-hANP selectively relaxed the high K+-contracted renal artery strip as compared with the basilar, coronary and femoral arterial strips. Intravenous alpha-hANP also increased urine volume and urinary excretion of electrolytes at doses, at which it increased renal blood flow and lowered systemic blood pressure without changing heart rate. It is concluded that alpha-hANP has a vasodilatory property relatively specific for the renal artery, and that it possesses diuretic, natriuretic, kaliuretic, magnesiuretic, calciuretic and chloruretic activities concomitantly with a definite hypotensive activity.     

Role of NPR-C natriuretic receptor in nitric oxide system activation induced by atrial natriuretic peptide

Atrial natriuretic peptide (ANP) exerts its hypotensive, natriuretic and diuretic effects, almost in part, through the activation of nitric oxide synthase (NOS). The aim was to investigate the natriuretic receptor type and the signaling cascade involved in NOS activation induced by ANP. Male Wistar rats were sacrificed and NOS activity was determined in kidney, aorta and heart with L-[U14C]-arginine, as substrate. ANP and cANP (4-23), a selective NPR-C ligand, increased NOS activity in all tissues. ANP induced a more marked activation in aorta and kidney than cANP (4-23), but no difference in atria NOS activation was observed. NOS activity induced by both peptides was blunted by nifedipine (L-type channel blocker) and calmidazolium (calmodulin antagonist) in heart and aorta. In kidney, nifedipine and calmidazolium abolished NOS activity stimulated by cANP (4-23) but only partially inhibited NOS activity elicited by ANP. Gi inhibition with pertussis toxin abolished NOS activity stimulated by ANP and cANP in atria but only partially inhibited the increased NOS activity induced by ANP and cANP in kidney, aorta and ventricle. Our results show that NPR-C receptor would mediate the activation of NOS by ANP in atria. In kidney, aorta and ventricle, NOS activation would also involve NPR-A and/or B. ANP would interact with NPR-C coupled via Gi to activation Ca2+ -dependent NOS.     

The role of the C-terminal region of rat brain natriuretic peptide in receptor selectivity.

Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) have different C-terminal tail structures compared with the rather conservative ring structures which consist of 17 amino acid residues. To examine the different effects of the tail structures of ANP and BNP on their interaction with receptors, we synthesized several peptide analogs and measured their biological actions in three different assay systems. Deletion of the C-terminal tail from rat BNP did not effect the vasorelaxation activity against rat aorta, but it promoted cGMP production in cultured rat aortic smooth muscle cells (RASMC). Deletion of the C-terminal tail from rat ANP diminished both vasorelaxant and cGMP producing activities. In a binding competition assay with RASMC and [125I]rat ANP-(1-28), the competition activities of both ANP and BNP were greatly reduced by C-terminal deletion. In addition, we obtained agonists with novel receptor selectivity.     

Atrial natriuretic peptide influence on nitric oxide system in kidney and heart

Atrial natriuretic peptide (ANP) and nitric oxide (NO) induce diuresis, natriuresis and diminish vascular tone. Our previous studies showed NO system is involved in ANP hypotensive effect. The aim was to investigate ANP effects on renal and cardiac NO-synthase (NOS) activity. Rats were divided into two groups: group I, infused with saline (1 h, 0.05 ml/min); group II, received ANP bolus (5 microg/kg)+ANP infusion (1 h, 0.2 microg/kg x min). NADPH-diaphorase activity (NADPH-d) was determined in kidney and heart. NOS catalytic activity was determined in renal medulla and cortex and cardiac atria and ventricle by measuring the conversion of l-[U(14)C]-arginine to l-[U(14)C]-citrulline. In group I, NOS activity was determined in basal conditions and plus 1 microM ANP and in group II, NOS activity was determined in basal conditions. NADPH-d was higher in group II than in group I in glomeruli, proximal tubule, cortical and medullar collecting duct, right atria and left ventricle. NOS activity was increased by in vitro ANP addition and, in vivo, ANP infusion in all the studied tissues. ANP treatment increases renal and cardiac NO synthesis. This effect would be independent on the hemodynamic changes induced by ANP. The activation of NO pathway would be one of the mechanisms involved in diuretic, natriuretic and hypotensive effects of ANP.     

Atrial peptides and the renal response to hypervolemia in nephrotic rats

Immunoreactive atrial natriuretic peptide (iANP) levels in plasma of edematous rats with an experimental nephrotic syndrome produced by the injection of puromycin aminonucleoside (PAN) were not different from those in untreated rats. To test the ability of nephrotic rats to secrete iANP in response to a volume stress, the rats were subjected to 20% expansion of their estimated blood volumes using blood from donor rats. PAN-treated rats had very small natriuretic and diuretic responses compared with untreated rats; however, there was no difference in the secretory response of iANP, which increased approximately threefold in each group. There were highly significant correlations between changes in plasma iANP and changes in right atrial pressure in both normal and nephrotic rats. Nephrotic rats that were infused with synthetic ANP showed only a very small natriuretic and diuretic response compared with normal rats, and no change in glomerular filtration rate. The hypotensive response was still present, however. Urine concentration in nephrotic rats was much lower than in controls and was not increased by exogenous arginine vasopressin. It is concluded that the absence of a normal natriuretic and diuretic response to hypervolemia in PAN-treated rats is not caused by a failure to secrete ANP but might be a result of an intrarenal defect that makes their kidneys unresponsive.     

Amino acid sequence and relative biological activity of eel atrial natriuretic peptide

A peptide exhibiting vasodepressor and natriuretic activities in rats was isolated from eel atria, and its primary structure was determined as H-Ser-Lys-Ser-Ser-Ser-Pro-Cys-Phe-Gly-Gly-Lys-Leu-Asp-Arg-Ile-Gly-Ser-Tyr-Ser- Gly-Leu-Gly-Cys-Asn-Ser-Arg-Lys-OH. This peptide, termed eel atrial natriuretic peptide (ANP), has sequence homology of 59% to mammalian (human or rat) ANP, 52% to fowl ANP, and 46% to frog ANP. When the biological activity of synthetic eel ANP was compared with that of human ANP, the eel peptide was 110 times more potent for the vasodepressor activity in eels, nearly equipotent for the vasodepressor activity in quails, and 20 times less potent for the vasodepressor and natriuretic activity in rats.