Effect of atrial natriuretic peptide on renin release in rat isolated glomeruli

Effects of atrial natriuretic peptide (ANP) on renin release in isolated rat glomeruli were investigated. ANP suppressed renin release by 25% at 5 x 10(-8) M when glomeruli were incubated in a medium containing 1.26 mM calcium (p = 0.0019). When glomeruli were incubated in a calcium free medium containing 2 mM EGTA, ANP suppressed stimulated renin release significantly at 5 x 10(-8) and 5 x 10(-9) M by 25% (p = 0.0204, and p = 0.0101, respectively). These results indicate that ANP suppresses renin release in a dose dependent manner, probably through a calcium independent process.     

Stimulation of guanylate cyclase by atrial natriuretic factor in isolated human glomeruli

A 23 amino acid synthetic peptide fragment of atrial natriuretic factor (ANF) stimulated guanylate cyclase activity in isolated human glomeruli in a concentration- and time-dependent manner. ANF activated particulate guanylate cyclase whereas it had no effect on soluble guanylate cyclase. These results demonstrate that the glomerulus is a target structure for ANF in humans. They also suggest that ANF-induced increase in glomerular filtration rate is due to a direct effect of this peptide on the glomerular cells mediated by activation of glomerular guanylate cyclase.     

利钾尿肽和心钠素在自发性高血压大鼠肾内的降解代谢

利钾尿肽 (ｋａｌｉｕｒｅｔｉｃｐｅｐｔｉｄｅ ,ＫＰ)是近年发现的与心钠素 (ａｔｒｉａｌｎａｔｒｉｕｒｅｔｉｃｐｅｐｔｉｄｅ ,ＡＮＰ)源于同一前体的具有 2 0个氨基酸的生物活性多肽。它不仅具有和心钠素一样的利尿、舒张血管、抑制肾素一血管紧张素系统的作用 ,还具有抑制心肌Ｎａ -Ｋ ＡＴＰ酶的作用 ,在调节机体血压和高血压发病中有重要意义。我们最近的研究发现 ,自发性高血压大鼠 (ｓｐｏｎｔａｕｅｏｕｓｌｙｈｙｐｅｒｔｅｎｓｉｖｅｒａｔ,ＳＨＲ)循环血液内的ＫＰ水平显著高于正常对照组Ｗｉｓｔａｒ Ｋｙｏｔｏ大鼠 (Ｗ…     

Immunohistochemical localization of atrial natriuretic peptide receptor in bovine kidney and lung

Receptors for atrial natriuretic peptide (ANP) were localized in the alveoli and bronchiolar smooth muscle cells of bovine lung and in podocytes of the kidney by immunofluorescence and immunoperoxidase methods. Two specific antisera were raised against the ANP receptor purified from bovine lung plasma membranes: anti-Rc 140 and anti-Rc 70. Anti-Rc 140 was raised against the 140 KD native receptor having a homodimeric structure, and anti-Rc 70 was elicited by immunizing a rabbit with the 70 KD reduced subunits. Essentially identical staining patterns were obtained with both antisera. Identification of ANP receptor sites would provide useful information in understanding the pulmonary and renal actions of ANP.     

Lack of inhibition by atrial natriuretic factor on cyclic AMP levels in single nephron segments and the glomerulus

Recently an inhibitory effect of atrial natriuretic factor (ANF) on the adenylate cyclase system has been reported in vascular tissue. In seeking similar affects in renal tissue, we studied the effect of ANF on cyclic AMP levels in single nephron segments and in glomeruli from the rat. Individual nephron segments or glomeruli were incubated in the presence of a phosphodiesterase inhibitor, with or without parathyroid hormone (PTH) or arginine vasopressin (AVP) and varying concentrations of ANF at 37 degrees C for 2 min. The capacity for alpha 2-adrenoceptor inhibition of adenylate cyclase was demonstrated in the proximal convoluted tubule, cortical collecting tubule and in glomeruli. Nevertheless, ANF could not inhibit cAMP formation in any of these nephron segments nor in the glomerulus. Thus, unlike the vasculature, ANF has no inhibitory effect on cAMP formation in these renal tissues.     

Synthesis of nucleic acids and localization of atrial natriuretic peptide in crayfish haemocytes

Three types of cells circulate in the haemolymph of the crayfish Astacus astacus, i.e., agranular haemocytes (HCs I), small-granule haemocytes (HCs II), and large-granule haemocytes (HCs III). Their proliferation, differentiation, and function remain poorly understood. Using light and electron microscopic autoradiography with [³H]-thymidine, we found that only HCs I are capable of DNA synthesis and mitosis whereas HCs II and HCs III are replicatively inactive. To verify whether HCs I are proliferating progenitor cells for granular HCs, we have analyzed autographs of the HC population 1, 2, 7, and 21 days after a single [3H]-thymidine administration. Contrary to our expectations, we have failed to find labeled HCs II and HCs III. These findings have raised doubts as to the capacity of HCs I to differentiate into two other types of HCs. With the use of ³H-uridine autoradiography, it was found that RNA synthesis was the most active in HCs I and 2 and 4 times lower in HCs II and HCs III, respectively. ANP-like immunoreactivity was revealed in large granules of the HCs III by electron microscopic immunocytochemistry. We assume that the presence of ANP in secretory granules extends the possible functions of crayfish HCs and suggests their participation in the regulation of the watersalt balance and immune response.     

Right atrial predominance of atrial natriuretic peptide secretion in isolated perfused rat atria.

In order to investigate the regulatory mechanism for the atrial release of atrial natriuretic peptide (ANP), a perfused rabbit atrial model was devised. In the present experiments, the effect of a reduction in atrial distension on the immunoreactive ANP (irANP) secretion was investigated and compared in the perfused right and left atria of rats. Elevations in right and left atrial pressure resulted in proportional increases in the volume of atrial distension-reduction which was larger in the right than in the left atria. The basal rate of irANP secretion was higher in the right than in the left atria. Increases in the volume of atrial distension-reduction resulted in proportional increases in irANP secretion in both atria. Increment in irANP secretion in response to a reduction in atrial distension was significantly higher in the right than in the left atria. Higher rate of irANP secretion in response to unit volume change was observed in the right atria. Increases in the volume of atrial distension-reduction resulted in accentuated irANP responses in the right atrium. IrANP content was significantly higher in the right than in the left atria. The results suggest that the right atrium is a predominant site in ANP secretion in rats.     

Immunocytochemical localization of atrial natriuretic peptide, vessel dilator, long-acting natriuretic peptide, and kaliuretic peptide in human pancreatic adenocarcinomas.

We recently found that four peptide hormones synthesized by the same gene completely inhibit the growth of human pancreatic adenocarcinomas in athymic mice. The present immunocytochemical investigation was designed to determine where in the adenocarcinomas these peptide hormones localize. Atrial natriuretic peptide, vessel dilator, long-acting natriuretic peptide, and kaliuretic peptide localized to the cytoplasm and nucleus of the human pancreatic adenocarcinomas, which is consistent with their ability to decrease DNA synthesis in the nucleus of this cancer. In this first investigation of where these peptide hormones with anticancer effects localize in any cancer, these peptide hormones also localized to the endothelium of capillaries and fibroblasts within these cancers. This is the first demonstration of growth-inhibiting peptide hormones localizing to the nucleus, where they inhibit DNA synthesis and may interact with growth-promoting hormones that localize there as the etiology of their ability to inhibit the growth of adenocarcinomas both in vitro and in vivo.     

Immunohistochemical localization of atrial natriuretic peptide in the developing and adult mammalian kidney

The discovery, within the last decade, of atrial natriuretic peptide (ANP), a family of peptides with natriuretic/diuretic and vasorelaxant properties, has prompted much research into the mechanisms and sites of action of ANP within the kidney. In the present study, ANP was localized in the kidneys of several mammalian species by immunohistochemical techniques 1) to identify possible sites of synthesis; 2) to compare the localization of ANP to known physiological effects; 3) to determine species differences, if any, in ANP localization; and 4) to study the development of ANP immunoreactivity in the fetal and neonatal rat kidney. Using an antibody against rat ANP, IV, ANP was localized exclusively on the proximal convoluted tubule (PCT) brush border and within intercalated cells of the outer medullary and cortical collecting tubules and ducts of adult mouse, rat, pig, monkey, and human kidneys. The development of ANP immunoreactivity paralleled the differentiation and maturation of collecting duct epithelium in rat fetal kidney. Atrial natriuretic peptide found within intercalated cells of the cortical and outer medullary collecting ducts may be the result of endogenous synthesis and, following secretion, may be available to receptors in the inner medullary collecting ducts.     

Heterogeneity in responses of isolated monkey arteries and veins to atrial natriuretic peptide

Regional differences in responses of isolated monkey arteries and veins to atrial natriuretic peptide were investigated by recording isometric tension. Addition of atrial natriuretic peptide (4 X 10(-12) to 4 X 10(-8) M) produced a concentration-dependent relaxation in isolated monkey arteries and veins. No significant difference was observed between the responses to rat and human atrial natriuretic peptides. A marked heterogeneity in responses to rat atrial natriuretic peptide, however, was observed in arterial preparations. The decreasing order of the response was as follows: renal greater than pulmonary greater than femoral = mesenteric greater than coronary greater than middle cerebral greater than basilar arteries. A heterogeneity in the relaxation produced by atrial natriuretic peptide was also observed in monkey veins. The decreasing order of the response was as follows: pulmonary greater than mesenteric = portal greater than femoral greater than renal = inferior caval veins. On the other hand, 10(-5) M sodium nitroprusside caused a maximal relaxation in all monkey arteries and veins used. In the middle cerebral, basilar, and coronary arteries, the relaxant effects of rat atrial natriuretic peptide on KCl-induced contraction were significantly smaller than those on the preparations contracted by an agonist such as prostaglandin F2 alpha. These results suggest that there exist profound regional vasorelaxant selectivities of atrial natriuretic peptide in isolated monkey arteries and veins.     

Synthesis of nucleic acids and localization of atrial natriuretic peptide in the crayfish haemocytes

Three types of cells circulate in haemolymph of the crayfish Astacus astacus: agranular haemocytes (HCs I), small-granule haemocytes (HCs II) and large-granule haemocytes (HCs III). Their proliferation, differentiation and function remain poorly understood. By means of light and electron microscopic autoradiography using [3H]-thymidine, we have revealed that only HCs I are capable of DNA synthesis and mitosis whereas HCs II and HCs III are replicatively inactive. To determine whether the HCs I are proliferating progenitor cells for the granular HCs, we have analyzed autographs of HC population in 1, 2, 7 and 21 days after a single [3H]-thymidine administration. Contrary to the expectation, we have failed to find labeled HCs II and HCs III. These findings raise doubts on the capacity of the HCs I to differentiate into two other types of HCs. By autoradiography using 3H-uridine, it has been detected that intensity of the RNA synthesis was the greatest in HCs I and less by a factor of two and four in HCs II and HCs III, respectively. Additionally, by EM immunocytochemistry, ANP-like immunoreactivity was revealed in the large granules of the HCs III. We assume that availability of ANP in secretory granules extends the possible functions of the crayfish HCs and suggests their participation in regulation of water-salt balance and immune responses.     

Oxidative stress augments the secretion of atrial natriuretic peptide in isolated rat atria

Reactive oxygen species (ROS) play a role in cardiovascular diseases such as hypertension and heart failure. The objective of the present study was to investigate the role of endogenous ROS in atrial hemodynamics and ANP secretion in isolated perfused beating rat atria. Pyrogallol (a generator of superoxide anion, 0.1, 1 mM) or hydrogen peroxide (0.1, 1, 10, 30 mM) was perfused into atria paced at 1.2 Hz. Pyrogallol and hydrogen peroxide stimulated ANP secretion and concentration in a dose-dependent manner and dramatically decreased atrial contractility and translocation of extracellular fluid. The stimulatory effect of pyrogallol and hydrogen peroxide on ANP secretion was attenuated by the pretreatment with ascorbic acid (an antioxidant; 1 mM) and cariporide (an inhibitor of the Na⁺/H⁺ exchanger; 1 μM) but negative inotropic effect was not changed. U120 (a MAPK^erk pathway inhibitor; 10 μM) attenuated the stimulatory effect of hydrogen peroxide on ANP secretion. However, U120 augmented negative inotropic effect and stimulatory effect of ANP concentration induced by pyrogallol. Antioxidant such as N-acetyl cystein, gallate, propyl gallate, or ellagic acid did not cause any significant changes in atrial parameters. These results suggest that intracellular - formed ROS stimulates ANP secretion partly through activation of MAPK^erk pathway and Na⁺/H⁺ exchanger.     

Release of atrial natriuretic peptide by atrial distension

A heterologous radioimmunoassay was used to measure the concentration of immunoreactive atrial natriuretic peptide (iANP) in plasma from the femoral artery of eight chloralose anaesthetized dogs. Mitral obstruction which increased left atrial pressure by 11 cmH2O increased plasma iANP from 97 +/- 10.3 (mean +/- SE) to 135 +/- 14.3 pg/mL. Pulmonary vein distension increased heart rate but did not increase plasma iANP. Bilateral cervical vagotomy and administration of atenolol (2 mg/kg) did not prevent the increase in iANP with mitral obstruction. Samples of blood from the coronary sinus had plasma iANP significantly higher than simultaneous samples from the femoral artery confirming the cardiac origin of the iANP. Release of iANP depends on direct stretch of the atrium rather than on a reflex involving left atrial receptors.     

血管钠肽、 C型钠尿肽和心房钠尿肽舒血管作用的对比

本实验采用离体血管灌流方法,观察和比较血管钠肽（ＶＮＰ）,Ｃ型钠尿肽（ＣＮＰ）和心房钠尿肽（ＡＮＰ）对大鼠肺动脉,腹主动脉和腹腔静脉的舒张作用。．结果表明,ＶＮＰ,ＣＮＰ和ＡＮＰ对离体大鼠的保留内皮与去内皮的肺动脉,腹主动脉和腹腔静脉均有浓度依赖性舒张作用。     

Characterization of atrial natriuretic peptide degradation by cell-surface peptidase activity on endothelial cells

Atrial natriuretic peptide (ANP) is a fluid-regulating peptide hormone that promotes vasorelaxation, natriuresis, and diuresis. The mechanisms for the release of ANP and for its clearance from the circulation play important roles in modulating its biological effects. Recently, we have reported that the cell surface of an endothelial cell line, CPA47, could degrade ¹²⁵I-ANP in the presence of EDTA. In this study, we have characterized this degradation of ¹²⁵I-ANP. The kinetics of ANP degradation by the surface of CPA47 cells were first order, with a K_m of 320 ± 60 nM and V_max of 35 ± 14 pmol of ANP degraded/10 min/10⁵ cells at pH 7.4. ANP is degraded by the surface of CPA47 cells over a broad pH range from 7.0–8.5. Potato carboxypeptidase inhibitor and bestatin inhibited ¹²⁵I-ANP degradation, suggesting that this degradative activity on the surface of CPA47 cells has exopeptidase characteristics. The selectivity of CPA47 cell-surface degradation of ANP was demonstrated when ¹²⁵I-ANP degradation was inhibited in the presence of neuropeptide Y and angiotensin I and II but not bradykinin, bombesin, endothelin-1, or substance P. The C-terminal amino acids phe²⁶ and tyr²⁸ were deduced to be important for ANP interaction with the cell-surface peptidase(s) based on comparison of the IC₅₀ of various ANP analogues and other natriuretic peptides for the inhibition of ANP degradation. These data suggest that a newly characterized divalent cation-independent exopeptidase(s) that selectively recognizes ANP and some other vasoactive peptides exists on the surface of endothelial cells.     

Immunocytochemical localization of atrial natriuretic peptide in endothelial and granular cells of the heart of lophotrochozoa

In parallel with contraction, vertebrate cardiomyocytes perform endocrine function and produce natriuretic peptides (NP)--ANP and BNP--involved in cardiovascular homeostasis maintenance. ANP-like peptides have been reported also in hearts of some invertebrates, however, their cellular localization was not determined. By electron microscopical immunocytochemistry with polyclonal monospecific antibodies raised against ANP and protein A-gold technique, we have localized ANP-like immunoreactivity in granules within endothelial cells in the heart of the brachiopod Rhynchonella psittacea, the polychaete Arenicola marina, and the gastropod mollusc Achatina fulica--all being representatives of the major phylogenetic group Lophotrochozoa. ANP-like immunoreactivity was also revealed in one of 3 morphologically distinguishable types of granules in the snail heart granular cells. By electron microscopical autoradiography with the use of [3H]-thymidine, the ability for DNA synthesis was demonstrated in heart endothelial cells of the investigated animals. Forms of NP-system organization in hearts of Lophotrochozoa and Vertebrates, and close histogenetic relationships of endothelial and granular cells in the snail heart are discussed.     

Characteristics of distension-induced release of immunoreactive atrial natriuretic peptide in isolated perfused rabbit atria

Atrial pressure- or distension-induced release of atrial natriuretic peptide (ANP) has been considered as an important regulatory mechanism of ANP release in cardiac atria. A new technique to permit graded continuous atrial distension has been developed in an isolated perfused single rabbit atrium. Graded atrial distension was induced by changing the elevation of the outflow catheter tip. Intra-atrial volume expansion resulted in an increase in immunoreactive ANP release. The graded increase in atrial distension from 43.9 +/- 10.2 to 207.7 +/- 29.1 microliter resulted in 6.2-27.1-fold increases in volume-dependent immunoreactive ANP release. A rise in immunoreactive ANP release induced by increasing atrial distension did not occur in the state of atrial distension but occurred only after return to the reduced distension. However, in the case of atrial distension with pacing, an increase in immunoreactive ANP release was observed during atrial distension with pacing and after return to the basal level. The present study shows that the new technique is applicable to the study of the 'stretch-secretion coupling' mechanism of ANP release in vitro, and that the more important factor involved in the release of immunoreactive ANP induced by atrial distension may be the atrial reduction to basal level after distension rather than the stretch itself.