Atrial natriuretic peptide induces natriuretic peptide receptor-cGMP-dependent protein kinase interaction

Circulating natriuretic peptides such as atrial natriuretic peptide (ANP) counterbalance the effects of hypertension and inhibit cardiac hypertrophy by activating cGMP-dependent protein kinase (PKG). Natriuretic peptide binding to type I receptors (NPRA and NPRB) activates their intrinsic guanylyl cyclase activity, resulting in a rapid increase in cytosolic cGMP that subsequently activates PKG. Phosphorylation of the receptor by an unknown serine/threonine kinase is required before ligand binding can activate the cyclase. While searching for downstream PKG partners using a yeast two-hybrid screen of a human heart cDNA library, we unexpectedly found an upstream association with NPRA. PKG is a serine/threonine kinase capable of phosphorylating NPRA in vitro; however, regulation of NPRA by PKG has not been previously reported. Here we show that PKG is recruited to the plasma membrane following ANP treatment, an effect that can be blocked by pharmacological inhibition of PKG activation. Furthermore, PKG participates in a ligand-dependent gain-of-function loop that significantly increases the intrinsic cyclase activity of the receptor. PKG translocation is ANP-dependent but not nitric oxide-dependent. Our results suggest that anchoring of PKG to NPRA is a key event after ligand binding that determines distal effects. As such, the NPRA-PKG association may represent a novel mechanism for compartmentation of cGMP-mediated signaling and regulation of receptor sensitivity.     

Reduced cGMP signaling activates NF-kappaB in hypertrophied hearts of mice lacking natriuretic peptide receptor-A

Mice lacking natriuretic peptide receptor-A (NPRA) develop progressive cardiac hypertrophy and congestive heart failure. However, the mechanisms responsible for cardiac hypertrophic growth in the absence of NPRA signaling are not yet known. We sought to determine the activation of nuclear factor-kappaB (NF-kappaB) in Npr1 (coding for NPRA) gene-knockout (Npr1-/-) mice exhibiting cardiac hypertrophy and fibrosis. NF-kappaB binding activity was 4-fold greater in the nuclear extract of Npr1-/- mutant mice hearts as compared with wild-type (Npr1+/+) mice hearts. In parallel, inhibitory kappaB kinase-beta activity and IkappaB-alpha protein phosphorylation were also increased 3- and 4-fold, respectively, in hypertrophied hearts of mutant mice. cGMP levels were significantly reduced 5-fold in plasma and 10-fold in ventricular tissues of mutant mice hearts relative to wild-type controls. The present findings provide direct evidence that ablation of NPRA/cGMP signaling activates NF-kappaB binding activity associated with hypertrophic growth of mutant mice hearts.     

Photolabeling study of the ligand binding domain of natriuretic peptide receptor A: development of a model

Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) are loop-shaped peptidic hormones that have multiple actions on body fluid homeostasis. Their physiological effects are mediated through the activation of their receptor, natriuretic peptide receptor A (NPRA). This receptor is a member of the membrane guanylyl cyclase family and catalyzes cyclic guanosine monophosphate (cGMP) production following its activation. To map the binding site of human NPRA, we applied the methionine proximity assay method to this receptor. We photolabeled NPRA mutants, presenting a single methionine in the binding domain of the receptor, and used benzoylphenylalanine- (Bpa-) substituted peptides at positions 0, 3, 18, 26, and 28 of the ligand. We identified that the N-terminus of the peptide is interacting with the region between Asp(177) and Val(183) of the receptor. Arg(3) is interacting in the vicinity of Phe(172). Leu(18) binds close to Val(116). Phe(26) binds in the vicinity of His(195), and the C-terminal Tyr(28) is located close to Met(173). We next proceeded with photolabeling of a dual Bpa-substituted peptide and showed that the N-terminus and Leu(18) interact with opposite receptor subunits. On the basis of our results, a molecular model of peptide-bound NPRA was developed by homology modeling with the C-type natriuretic peptide- (CNP-) bound natriuretic peptide receptor C (NPRC) crystal structure. The model has been validated by molecular dynamics simulations. Our work provides a rational basis for interpreting and predicting natriuretic peptide binding to the human NPRA.     

血管钠肽对离体人乳内动脉的舒张作用

为了研究血管钠肽(VNP)对人乳内动脉(human intramammary artery,HIMA)的舒张作用及其机制,采用离体血管灌流的方法,观察VNP对内皮完整和去内皮HIMA的舒张作用,以及HS—142—1、TEA、8—Br—cGMP和镁蓝(MB)对这一过程的影响。实验中观察到,VNP(0．0001—1μmol/L)可引起剂量依赖性的舒张效应,且无内皮依赖性;8—Br—cGMP(0．1—1000μmol/L)也可引起剂量依赖性的血管舒张效应。钠尿肽鸟苷酸环化酶(guanylate cyclase,GC)受体的特异性阻断剂HS—142—1(20μmol/L)使VNP舒张HIMA的作用几乎完全消失。MB是GC的抑制剂,10μmol/L的MB不但使VNP舒张HIMA的作用完全消失,而且可增强HIMA对去甲肾上腺素(NE)产生的收缩反应。钙激活钾通道(KCa)的阻断剂TEA(1mmol/L)可减弱(但是不完全阻断)VNP的舒血管作用。上述结果表明,VNP对HIMA具有不依赖内皮的舒张作用;此作用是通过作用于平滑肌细胞的钠尿肽GC受体,引起细胞内的cGMP水平升高实现的,并且与Kca有关。     

C型钠尿肽及其受体在急性肺损伤大鼠肺组织的表达变化及其意义

目的了解C型钠尿肽及其受体NPRB在急性肺损伤大鼠肺组织中的表达变化规律。方法采用LPS注射建立ALI大鼠动物模型。将动物分为生理盐水组(N组),LPS干预1 h组(LPS 1 h组),LPS干预3 h组(LPS 3 h组),LPS干预6 h组(LPS 6 h组),通过RT-PCR检测各组大鼠肺组织CNP及NPRB mRNA的表达情况,以及免疫组化检测各组大鼠NPRB的表达变化,以生理盐水组作为阴性对照。结果正常大鼠肺组织可表达CNP及NPRB,LPS干预后,CNP显著升高,LPS 6 h达到高峰,与对照组比较有显著性差异(P0.05);相反,NPRB在LPS干预后出现表达降低,与对照组比较有显著性差异(P0.05)。结论CNP与NPRB的表达变化可能是导致肺损伤加重的重要原因之一。     

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。     

Subcellular trafficking of guanylyl cyclase/natriuretic peptide receptor-A with concurrent generation of intracellular cGMP

Atrial natriuretic peptide (ANP) activates guanylyl cyclase/natriuretic peptide receptor-A (GC-A/NPRA), which lowers blood pressure and blood volume. The objective of the present study was to visualize internalization and trafficking of enhanced GFP (eGFP)-tagged NPRA (eGFP–NPRA) in human embryonic kidney-293 (HEK-293) cells, using immunofluorescence (IF) and co-immunoprecipitation (co-IP) of eGFP–NPRA. Treatment of cells with ANP initiated rapid internalization and co-localization of the receptor with early endosome antigen-1 (EEA-1), which was highest at 5 min and gradually decreased within 30 min. Similarly, co-localization of the receptor was observed with lysosome-associated membrane protein-1 (LAMP-1); however, after treatment with lysosomotropic agents, intracellular accumulation of the receptor gradually increased within 30 min. Co-IP assays confirmed that the localization of internalized receptors occurred with subcellular organelles during the endocytosis of NPRA. Rab 11, which was used as a recycling endosome (Re) marker, indicated that ∼20% of receptors recycled back to the plasma membrane. ANP-treated cells showed a marked increase in the IF of cGMP, whereas receptor was still trafficking into the intracellular compartments. Thus, after ligand binding, NPRA is rapidly internalized and trafficked from the cell surface into endosomes, Res and lysosomes, with concurrent generation of intracellular cGMP.     

Intracellular trafficking and metabolic turnover ofligand-bound guanylyl cyclase/atrial natriuretic peptide receptor-A into subcellular compartments

Atrial natriuretic peptide (ANP) is the first described member of the natriuretic peptide hormone family. ANP elicits natriuretic, diuretic, vasorelaxant and antiproliferative effects, important factors in the control of blood pressure homeostasis. One of the principal loci involved in the regulatory action of ANP is the guanylyl cyclase-linked ANP-receptor which has been designated as NPRA, also referred to as GC-A, whose ANP-binding efficiency and guanylyl cyclase activity vary remarkably in different target tissues. However, the cellular and molecular basis of these activities and the functional expression and regulation of NPRA are not well understood. The mature form of receptor resides in the plasma membrane and consists of an extracellular ligand-binding domain, a single transmembrane-spanning region, and intracellular protein kinase-like homology and guanylyl cyclase catalytic domains. In this review, emphasis has been placed on the interaction of ANP with NPRA, the ligand-mediated endocytosis, trafficking, and subcellular distribution of ligand-receptor complexes from cell surface to the intracellular compartments. Furthermore, it is implicated that after internalization, the ANP/NPRA complexes dissociate into the subcellular compartments and a population of receptor recycles back to the plasma membrane. This is an interesting area of research in the natriuretic peptide receptor field because there is currently debate over whether ANP/NPRA complexes internalize at all or whether cell utilizes some other mechanisms to release ANP from the bound receptor molecules. Indeed, controversy exist since it has been previously reported by default that among the three natriuretic peptide receptors only NPRC internalizes with bound ligand. Hence, from a thematic standpoint it is clearly evident that there is a current need to review this subject and provide a consensus forum that establishes the cellular trafficking, sequestration and processing of ANP/NPRA complexes in intact cells. Towards this aim the cellular life-cycle of NPRA will be described in the context of ANP-binding, internalization, metabolic processing, and/or inactivation, down-regulation, and degradation of ligand-receptor complexes in model cell systems.     

Ligand-regulated internalization, trafficking, and down-regulation of guanylyl cyclase/atrial natriuretic peptide receptor-A in human embryonic kidney 293 cells.

We examined the kinetics of internalization, trafficking, and down-regulation of recombinant guanylyl cyclase/natriuretic peptide receptor-A (NPRA) utilizing stably transfected 293 cells expressing a very high density of receptors. After atrial natriuretic peptide (ANP) binding to NPRA, ligand-receptor complexes are internalized, processed intracellularly, and sequestered into subcellular compartments, which provided an approach to examining directly the dynamics of metabolic turnover of NPRA in intact cells. The translocation of ligand-receptor complexes from cell surface to intracellular compartments seems to be linked to ANP-dependent down-regulation of NPRA. Using tryptic proteolysis of cell surface receptors, it was found that approximately 40-50% of internalized ligand-receptor complexes recycled back to the plasma membrane with an apparent t(12) = 8 min. The recycling of NPRA was blocked by the lysosomotropic agent chloroquine, the energy depleter dinitrophenol, and also by low temperature, suggesting that recycling of the receptor is an energy- and temperature-dependent process. Data suggest that approximately 70-80% of internalized (125)I-ANP is processed through a lysosomal degradative pathway; however, 20-25% of internalized ligand is released intact into the cell exterior through an alternative mechanism involving an chloroquine-insensitive pathway. It is implied that internalization and processing of bound ANP-NPRA complexes may play an important role in mediating the biological action of hormone and the receptor protein. In retrospect, this could occur at the level of receptor regulation or through the initiation of ANP mediated signals. It is envisioned that the endocytotic pathway of ligand-receptor complexes of ANP-NPRA would lead to termination and/or diminished responsiveness of ANP in target cells.     

Vasonatrin peptide,a novel protector of dopaminergic neurons against the injuries induced by n-methyl-4-phenylpyridiniums

Vasonatrin peptide (VNP), a novel manmade natriuretic peptide, is known as a cardiovascular active substance. However, its neuroeffects are largely unknown. Here, cultured dopaminergic neurons from ventral mesencephalon of mouse were exposed to N-methyl-4-phenylpyridinium (MPP⁺), and the effects of VNP on the neurotoxicity of MPP⁺ were investigated. As a result, MPP⁺ caused injuries in the dopaminergic neurons. VNP significantly reduced the cytotoxicity of MPP⁺ by increasing axon number and length of dopaminergic neurons, and by enhancing the cell viability. Also, the MPP⁺-induced depolymerization of β-Tubulin III was attenuated by the treatment of VNP. In addition, VNP significantly increased the intracellular levels of cGMP. These effects of VNP were mimicked by 8-br-cGMP (a cell-permeable analog of cGMP), whereas inhibited by HS-142-1 (the antagonist of the particulate guanylyl cyclase-coupled natriuretic peptide receptors), or KT-5823 (a cGMP-dependent protein kinase inhibitor). Taken together, VNP attenuates the neurotoxicity of MPP⁺ via guanylyl cyclase-coupled NPR/cGMP/PKG pathway, indicating that VNP might be a new effective reagent in the treatment of neuron degeneration of dopaminergic neurons in Parkinson's disease (PD).     

Dendroaspis natriuretic peptide binds to the natriuretic peptide clearance receptor

Dendroaspis natriuretic peptide (DNP) is a newly-described natriuretic peptide which lowers blood pressure via vasodilation. The natriuretic peptide clearance receptor (NPR-C) removes natriuretic peptides from the circulation, but whether DNP interacts with human NPR-C directly is unknown. The purpose of this study was to test the hypothesis that DNP binds to NPR-C. ANP, BNP, CNP, and the NPR-C ligands AP-811 and cANP(4-23) displaced [(125)I]-ANP from NPR-C with pM-to-nM K(i) values. DNP displaced [(125)I]-ANP from NPR-C with nM potency, which represents the first direct demonstration of binding of DNP to human NPR-C. DNP showed high pM affinity for the GC-A receptor and no affinity for GC-B (K(i)>1000 nM). DNP was nearly 10-fold more potent than ANP at stimulating cGMP production in GC-A expressing cells. Blockade of NPR-C might represent a novel therapeutic approach in augmenting the known beneficial actions of DNP in cardiovascular diseases such as hypertension and heart failure.     

Natriuretic peptides inhibit adenylyl cyclase activity in dispersed eel gill cells

The effect of natriuretic peptides on forskolin-evoked adenylyl cyclase activity was investigated in dispersed gill cells from the Australian short-finned eel (Anguilla australis). Molecular cloning techniques were employed to identify the putative G-protein-activating motif within the intracellular domain of the eel natriuretic peptide C receptor. Eel ANP, eel CNP and the NPR-C-specific C-ANF inhibited the forskolin-stimulated production of cyclic AMP. This effect was abolished by pretreatment of cells with pertussis toxin. Eel VNP was without effect on adenylyl cyclase activity. PCR and molecular cloning indicated that the intracellular domain of A. australis NPR-C has the same amino acid sequence as Anguilla japonica. Alignment of these sequences with Rattus norvegicus NPR-C indicated conservation of the putative G-protein-activating motif BB...BBXXB (B=basic, X=nonbasic residues). These data suggest that branchially-expressed NPR-C may play a physiological role additional to that of ligand clearance.Abbreviations ANP atrial natriuretic peptide - CNP C-type natriuretic peptide - cAMP cyclic adenosine monophosphate - cGMP cyclic guanosine monophosphate - eANP-NH₂ amidated form of eel ANP - GC guanylyl cyclase - G_i inhibitory G-protein - IBMX isobutylmethylxanthine - NP natriuretic peptide - NPR natriuretic peptide receptor - PCR polymerase chain reaction - PTX pertussis toxin - VNP ventricular natriuretic peptideCommunicated by I.D. Hume     

Natriuretic peptide receptor A activation stabilizes a membrane-distal dimer interface

We have shown previously (Rondeau, J.-J., McNicoll, N., Gagnon, J., Bouchard, N., Ong, H., and De Léan, A. (1995) Biochemistry 34, 2130-2136) that atrial natriuretic peptide (ANP) stabilizes a dimeric form of the natriuretic peptide receptor A (NPRA) by simultaneously interacting with both receptor subunits. However, the first crystallographic study of unliganded NPRA extracellular domain documented a V-shaped dimer involving a membrane-proximal dimer interface and separate binding sites for ANP on each monomer. We explored the possibility of an alternative A-shaped dimer involving a membrane-distal dimer interface by substituting an unpaired solvent-exposed cysteine for Trp(74) in the amino-terminal lobe of full-length NPRA. The predicted spacing between Trp(74) from both subunits drastically differs, depending on whether the V-shaped (84 A) or the A-shaped (8 A) dimer model is considered. In contrast with the expected results for the reported V-shaped dimer, the NPRA(W74C) mutant was constitutively covalently dimeric. Also, the subunits spontaneously reassociated following transient disulfide reduction by dithiothreitol and reoxidation. However, ANP could neither bind to nor activate NPRA(W74C). Permanent disulfide opening by reduction with dithiothreitol and alkylation with N-ethylmaleimide rescued ANP binding to NPRA(W74C). The NPRA mutant could be maintained as a covalent dimer while preserving its function by crosslinking with the bifunctional alkylating agent phenylenedimaleimides (PDM), the ortho-substituted oPDM being more efficient than mPDM or pPDM. These results indicate that the membrane-distal lobe of the NPRAM extracellular domains are dynamically interfacing in the unliganded state and that ANP binding stabilizes the receptor dimer with more stringent spacing at the dimer interface.     

The functional genomics of guanylyl cyclase/natriuretic peptide receptor-A: perspectives and paradigms

The cardiac hormones atrial natriuretic peptide and B-type natriuretic peptide (brain natriuretic peptide) activate guanylyl cyclase (GC)-A/natriuretic peptide receptor-A (NPRA) and produce the second messenger cGMP. GC-A/NPRA is a member of the growing family of GC receptors. The recent biochemical, molecular and genomic studies on GC-A/NPRA have provided important insights into the regulation and functional activity of this receptor protein, with a particular emphasis on cardiac and renal protective roles in hypertension and cardiovascular disease states. The progress in this field of research has significantly strengthened and advanced our knowledge about the critical roles of Npr1 (coding for GC-A/NPRA) in the control of fluid volume, blood pressure, cardiac remodeling, and other physiological functions and pathological states. Overall, this review attempts to provide insights and to delineate the current concepts in the field of functional genomics and signaling of GC-A/NPRA in hypertension and cardiovascular disease states at the molecular level.     

Comparative aspects of natriuretic peptide physiology in non-mammalian vertebrates: a review

The natriuretic peptide system is a complex family of peptides and receptors that is primarily linked to the maintenance of osmotic and cardiovascular homeostasis. A natriuretic peptide system is present in each vertebrate class but there are varying degrees of complexity in the system. In agnathans and chondrichthyians, only one natriuretic peptide has been identified, while new data has revealed that multiple types of natriuretic peptides are present in bony fish. However, it seems in tetrapods that there has been a reduction in the number of natriuretic peptide genes, such that only three natriuretic peptides are present in mammals. The peptides act via a family of guanylyl cyclase receptors to generate the second messenger cGMP, which mediates a range of physiological effects at key targets such as the gills, kidney and the cardiovascular system. This review summarises the current knowledge of the natriuretic peptide system in non-mammalian vertebrates and discusses the physiological actions of the peptides.Abbreviations ANP atrial natriuretic peptide - AVT arginine vasotocin - BNP brain natriuretic peptide - cDNA complementary deoxyribonucleic acid - CNP C-type natriuretic peptide - cAMP adenosine 3, 5 cyclic monophosphate - cGMP guanosine 3, 5 cyclic monophosphate - GC guanylyl cyclase - GFR glomerular filtration rate - mRNA messenger ribonucleic acid - NPR natriuretic peptide receptor - NPs natriuretic peptides - sCP salmon cardiac peptide - VIP vasoactive intestinal peptide - VNP ventricular natriuretic peptide Communicated by I.D. Hume     

Structure, signaling mechanism and regulation of the natriuretic peptide receptor guanylate cyclase

Atrial natriuretic peptide (ANP) and the homologous B-type natriuretic peptide are cardiac hormones that dilate blood vessels and stimulate natriuresis and diuresis, thereby lowering blood pressure and blood volume. ANP and B-type natriuretic peptide counterbalance the actions of the renin-angiotensin-aldosterone and neurohormonal systems, and play a central role in cardiovascular regulation. These activities are mediated by natriuretic peptide receptor-A (NPRA), a single transmembrane segment, guanylyl cyclase (GC)-linked receptor that occurs as a homodimer. Here, we present an overview of the structure, possible chloride-mediated regulation and signaling mechanism of NPRA and other receptor GCs. Earlier, we determined the crystal structures of the NPRA extracellular domain with and without bound ANP. Their structural comparison has revealed a novel ANP-induced rotation mechanism occurring in the juxtamembrane region that apparently triggers transmembrane signal transduction. More recently, the crystal structures of the dimerized catalytic domain of green algae GC Cyg12 and that of cyanobacterium GC Cya2 have been reported. These structures closely resemble that of the adenylyl cyclase catalytic domain, consisting of a C1 and C2 subdomain heterodimer. Adenylyl cyclase is activated by binding of G(s)α to C2 and the ensuing 7° rotation of C1 around an axis parallel to the central cleft, thereby inducing the heterodimer to adopt a catalytically active conformation. We speculate that, in NPRA, the ANP-induced rotation of the juxtamembrane domains, transmitted across the transmembrane helices, may induce a similar rotation in each of the dimerized GC catalytic domains, leading to the stimulation of the GC catalytic activity.     

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.     

血管钠肽抑制异丙肾上腺素增强的大鼠心肌细胞钙瞬变

采用光谱荧光法研究血管钠肽(vasonatrin peptide,VNP)对心肌细胞内钙瞬变的作用及其机制,观察钠尿肽鸟苷酸环化酶(guanylate cyclase,GC)受体的特异性阻断剂(HS-142-1)、8-溴-环磷酸鸟苷(8-Br-cGMP)和镁蓝(methylene blue,MB)对心肌细胞内钙瞬变的影响。结果显示,异丙肾上腺素(isoproterenol,Iso)(10~(-10)～10~(-6)mol/L)可剂量依赖性地引起心肌细胞内钙瞬变增强,相对于对照组分别增强(13±8)%(P>0.05)、(26±13)%(P<0.05)、(66±10)%(P<0.01)、(150±10)%(P<0.01)和(300±25)%(P<0.01)。此效应可被β肾上腺素受体阻断剂普萘洛尔(10~(-6)mol/L)所阻断。VNP(10~(-10)～10~(-6)mol/L)可剂量依赖性地抑制Iso(10~(-8)mol/L)引起的心肌细胞内钙瞬变幅值的升高,相对于Iso(10~(-8)mol/L)分别减弱(99±3)%(P>0.05)、(96±2)%(P<0.05)、(84±6)%(P<0.01)、(66±3)%(P<0.01)和(62±3)%(P<0.01)。8-Br-cGMP(10~(-7)～10~(-3)mol/L)也可剂量依赖性地抑制Iso(10~(-8)mol/L)引起心肌细胞内钙瞬变的增强。HS-142-1(2×10~(-5)mol/L)使VNP的作用几乎完全消失。MB是GC的抑制剂,10~(-5)mol/L MB不但使VNP的作用完全消失,而且增强Iso对心肌细胞内钙瞬变的效应。VNP和HS-142-1本身对心肌细胞内钙瞬变无显著影响。而MB使心