AIMTo investigate the effect of vasonatrin peptide (VNP) on the expression of C-type natriuretic peptide receptor (NPR-C) in hypoxic rat hearts.

METHODSRats were divided randomly into three groups: control group, hypoxia group(3-28 d) and VNP (25-75 microg/kg per day) + hypoxia group. The plasma concentration of atrial natriuretic peptide (ANP) in rats was measured by the means of radioimmunoassay. Furthermore, quantitative PCR was used to examine the NPR-C mRNA level in rat hearts.

RESULTSThe plasma concentration ANP in rats was significantly higher than that of control group, and VNP (75 microg/kg per day) made it more higher. Hypoxia for 3 day of had no significant effect on the NPR-C mRNA level in rat hearts, while hypoxia for 7-28 d significantly increased the level of NPR-C mRNA in a time dependent manner. VNP (50-75 microg/kg per day) significantly reduced the NPR-C mRNA level in rat hearts in a dose dependent manner.

CONCLUSIONVNP increases the plasma concentration of ANP in hypoxic rats. Hypoxia can increase expression of NPR-C in rat hearts significantly, which can be inhibited by VNP.

Animals ; Atrial Natriuretic Factor ; blood ; pharmacology ; Hypoxia ; metabolism ; Male ; Natriuretic Peptide, C-Type ; metabolism ; Natriuretic Peptides ; metabolism ; Rats ; Rats, Sprague-Dawley ; Receptors, Atrial Natriuretic Factor ; metabolism

The purpose of this study was to investigate the effects of vasonatrin peptide (VNP) on electrically-induced intracellular calcium ([Ca(2+)](i)) transient and mechanism of the effects in the cardiac myocytes. The [Ca(2+)](i) transient was measured with a fluoremetric method. The effects of HS-142-1, 8-Br-cGMP and methylene blue (MB) on [Ca(2+)](i) transient in cardiac myocytes were also determined. Isoproterenol (Iso) at 10(-10)~10(-6) mol/L augmented electrically-induced [Ca(2+)](i) transient dose-dependently, which was (13+/-8)% (P>0.05), (26+/-13)% (P< 0.05), (66+/-10)% (P<0.01), (150+/-10)% (P<0.01) and (300+/-25)% (P<0.01), respectively. These effects were blocked by an beta-adrenergic bloker propranolol (10(-6) mol/L). The effect of Iso (10(-8) mol/L) on [Ca(2+)](i) transient was attenuated in a dose-dependent manner by VNP at 10(-10)~10(-6) mol/L, which was (99+/-3)% (P>0.05), (96+/-2)% (P<0.05), (84+/-6)% (P<0.01), (66+/-3)% (P<0.01) and (62+/-3)% (P<0.01), respectively. 8-Br-cGMP (10(-7)~10(-3) mol/L) aslo attenuated 10(-8) mol/L Iso-induced [Ca(2+)](i) transient dose-dependent. The effect of VNP on [Ca(2+)](i) transient was almost abolished in the presence of HS-142-1 (2x10(-5) mol/L), an antagonist of the natriuretic peptide guanylate cyclase (GC) receptors. MB (10(-5) mol/L), an inhibitor of GC, not only blocked the effect of VNP in myocytes, but also augmented electrically-induced [Ca(2+)](i) transient. VNP and HS-142-1 themselves did not change the [Ca(2+)](i) transient in the cardiac myocytes significantly. But MB augmented the [Ca(2+)](i) transient in the cardiac myocytes significantly. These results suggest that VNP attenuates [Ca(2+)](i) transient induced by Iso. This effect is possibly achieved by binding VNP with the natriuretic peptide GC receptors in the myocytes, leading to an increase in intracellular cGMP.
Animals ; Atrial Natriuretic Factor ; pharmacology ; Calcium ; metabolism ; Calcium Channels ; metabolism ; Cyclic GMP ; metabolism ; Depression, Chemical ; Female ; Guanylate Cyclase ; metabolism ; Isoproterenol ; pharmacology ; Male ; Myocytes, Cardiac ; metabolism ; Rats ; Receptors, Atrial Natriuretic Factor ; metabolism

OBJECTIVETo investigate the role of C-type natriuretic peptide receptor (NPR-C) and large-conductance calcium-activated potassium channels (BK(Ca)) in brain natriuretic peptide (BNP) induced porcine coronary artery dilation.

METHODSPorcine coronary artery rings were obtained and treated with BNP (10(-6) mol/L), BNP + NPR-C antagonist cANF4-28 (10(-6) mol/L) and BNP + BK(Ca) blocker tetraethylammonium (TEA, 1 mmol/L). The vascular tone experiments were observed on 10 vessel segments. BK(Ca) current density was measured by the whole-cell patch clamp technique.

RESULTSThe maximum diastolic rate was similar between BNP group (68.51% ± 11.50%) and cANF4-28 + BNP group (65.67% ± 11.90%, P > 0.05) while significantly reduced in TEA + BNP group (28.87% ± 4.55%, all P < 0.05). When the holding potential was set at +60 mV, the BK(Ca) current density of BNP group was (78.48 ± 5.86) pA/pF, which was significantly higher than control group [(53.84 ± 4.55) pA/pF, P < 0.05], which was equally reduced in the TEA group and TEA + BNP group [(28.80 ± 2.76) pA/pF and (30.60 ± 3.88) pA/pF respectively, all P < 0.05 vs. control group].

CONCLUSIONBNP could relax the porcine coronary arterial smooth muscles by increasing BK(Ca) current, and this effect is not mediated by NPR-C.

Animals ; Coronary Vessels ; drug effects ; physiology ; Large-Conductance Calcium-Activated Potassium Channels ; physiology ; Natriuretic Peptide, Brain ; pharmacology ; Patch-Clamp Techniques ; Receptors, Atrial Natriuretic Factor ; physiology ; Swine

OBJECTIVEEndogenous hydrogen sulfide (H2S), a novel gasotransmitter in cardiovascular regulation, plays an important protective role in the development and progression of atherosclerosis (AS). This study was designed to explore the effects of H2S donor on the production of adrenomedullin (ADM) and atrial natriuretic peptide (ANP) in AS rats.

METHODSMale Sprague-Dawley rats were randomly divided into control group (n=10), AS group (n=10), and AS+NaHS group (n=10). Rats in the AS and AS+NaHS groups were given 3-day intraperitoneal injections of vitamin D3 and 8-week high-fat diet to induce AS, and the rats in the AS+NaHS group were intraperitoneally injected with H2S donor NaHS. Oil red O staining was applied to detect changes in the areas of the atherosclerotic plaques in the aortic root and the coronary artery; sulfide-sensitive electrode method was used to measure the plasma concentration of H2S. ADM and ANP levels in plasma were determined by radioimmunoassay.

RESULTSCompared with the control group, marked atherosclerotic plaques were observed in the aortic root and the coronary artery in AS rats. Moreover, plasma H2S level decreased significantly, ADM level increased, and ANP level decreased significantly in AS rats (P<0.01). However, after the treatment with H2S donor NaHS for 8 weeks, the above changes in AS rats were reversed, demonstrated by significantly reduced areas of the atherosclerotic plaques in both the aortic root and the coronary artery, significantly increased plasma H2S level, significantly decreased plasma ADM level, and significantly increased plasma ANP level (P<0.01).

CONCLUSIONSH2S plays an important regulatory effect on vasoactive peptides ADM and ANP in AS rats.

Adrenomedullin ; biosynthesis ; Animals ; Atherosclerosis ; metabolism ; pathology ; Atrial Natriuretic Factor ; biosynthesis ; Hydrogen Sulfide ; pharmacology ; Male ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo investigate the effects of atrial natriuretic peptide (ANP) on ischemia and reperfusion cochlea in guinea pigs.

METHODSThe guinea pigs were randomly allocated into four groups: experiment groups (A1 and B1) and control groups (A2 and B2). Cochlear ischemia and reperfusion was induced by thrombus and thrombolysis method. In experiment group A1, ANP was administered 10 min before the ischemic insult. In experiment group B1, ANP was administered at the beginning of reperfusion. In control groups, instead of ANP, normal sodium was injected. The blood flow of cochlea (CoBF) was monitored continuously with laser Doppler flow meter and the threshold of auditory brainstem response (ABR) was measured.

RESULTSBefore the induction of ischemia, the CoBF of experiment group A1 was higher than that of the control group A2. From the reperfusion moment to the end of the experiment, there was no difference between the CoBF of the two groups. In B1 and B2 groups, no difference could be seen between the two groups before the induction of ischemia. After reperfusion, the blood flow of control group B2 recovered to 70% of the base level, while the CoBF of experiment group B1 restored to almost the same level of the beginning. Before ischemia, the ABR threshold of the four groups had no difference. At 30 min of ischemia, the threshold of experiment group Al was lower than that of control group A2. And there was no difference in experiment group B1 and control group B2. At 30 min and 60 min of reperfusion, the threshold of experiment group B1 was significantly lower than that of control group B2. No difference could be seen between experiment group A1 and control group A2.

CONCLUSIONSAdministration of ANP at the beginning of reperfusion protects the cochlea from ischemia and reperfusion injury. The administration can not only increase the CoBF, but lower the ABR threshold.

Animals ; Atrial Natriuretic Factor ; pharmacology ; Cochlea ; blood supply ; drug effects ; physiopathology ; Disease Models, Animal ; Evoked Potentials, Auditory, Brain Stem ; Guinea Pigs ; Reperfusion Injury ; drug therapy ; physiopathology

AIMTo investigate how vasonatrin peptide (VNP) can attenuate the growth-promoting effect of hypoxia in cardiac fibroblasts cultured from neonatal rats.

METHODSThe cultured cardiac fibroblasts were divided randomly into four groups: control group, hypoxia group, hypoxia + VNP group and hypoxia + 8-Bromo-cGMP group. The growth of cardiac myocytes was measured by the means of MTT method. The effect of VNP on the intracellular level of cGMP and PCNA were measured by the means of radioimmunoassay and immunohistochemistry stain respectively.

RESULTSHypoxia (24 h) significantly increased the MTT A490nm value of cardiac fibroblasts (P < 0.05 vs control group). Both VNP (10(-7) mol/L) and 8-Bromo-cGMP (10(-3) mol/L) decreased MTT A490 nm value in cardiac fibroblast (P < 0.05 vs hypoxia group). VNP (10(-7) mol/L) increased the intracellular level of cGMP (P < 0.05 vs control and hypoxia group). Hypoxia (24 h) significantly increased the expression of proliferating cell nuclear antigen (PCNA) in cardiac myocytes (P < 0.05, vs control group), but VNP (10(-7) mol/L) decreased it.

CONCLUSIONVNP can attenuate hypoxia-induced growth-promoting effect in cardiac fibroblasts which is associated with the changes of cGMP and PCNA.

Animals ; Animals, Newborn ; Atrial Natriuretic Factor ; pharmacology ; Cell Hypoxia ; Cells, Cultured ; Cyclic GMP ; metabolism ; Myoblasts, Cardiac ; cytology ; drug effects ; Proliferating Cell Nuclear Antigen ; metabolism ; Rats ; Rats, Sprague-Dawley

The role of atrial natriuretic peptide (ANP) in the central regulation of the circulation is known to be a neurotransmitter or a neuromodulator, but its actions on baroreceptor reflex function are not fully resolved. The present study examined the role of ANP (6, 60 ng/0.2 microl) by direct microinjection into the hypothalamic paraventricular nucleus (PVN) in conscious rats. OPC-21268 (0.45 microg/3 microl), an antagonist of the V(1) receptor, was microinjected into the lateral ventricle to examine whether the effect of ANP on baroreflex sensitivity is mediated by vasopressin (VP). ANP significantly increased the baroreflex sensitivity, and OPC-21268 attenuated the increase of baroreflex sensitivity induced by ANP. Intravenous injections of ANP (60 ng/0.04 ml) did not affect baroreflex sensitivity. These results suggest that ANP in the PVN may produce a facilitative effect on baroreflex, and the effect may be via, at least in part, the central vasopressin.
Animals ; Atrial Natriuretic Factor ; pharmacology ; physiology ; Baroreflex ; drug effects ; physiology ; Male ; Microinjections ; Paraventricular Hypothalamic Nucleus ; physiology ; Random Allocation ; Rats ; Rats, Wistar

AIMTo investigate effect and mechanism of vasonatrin peptide (VNP) on Ca2+ activated K+ channels (K(Ca)) of vascular smooth muscle cells (VSMCs) isolated from rat mesentery arteries.

METHODSChanges of K(Ca) induced by VNP were measured by the means of whole cell recording mode of patch clamp, furthermore effects of HS-142-1(0.3 g/L), 8-Br-cGMP and methylene blue (MB) were observed.

RESULTSK(Ca) was significantly enhanced by VNP (10(-6) mol/L), which was mimicked by 8-Br-cGMP(10(-3) mol/L) and blocked completely by HS-142-1 or MB (2 x 10(-5) mol/L).

CONCLUSIONVNP increases K(Ca) of VSMCs isolated from rat mesenteric arteries, by binding with natriuretic peptide guanylate cyclase-coupled receptors and increasing the intracellular level of cGMP in VSMCs.

Animals ; Atrial Natriuretic Factor ; pharmacology ; Male ; Mesenteric Arteries ; cytology ; drug effects ; metabolism ; Muscle, Smooth, Vascular ; metabolism ; physiology ; Potassium Channels, Calcium-Activated ; drug effects ; metabolism ; Rats ; Rats, Sprague-Dawley

This paper was aimed to investigate the inhibitory effect of aconitine(AC) on angiotensin Ⅱ(Ang Ⅱ)-induced H9 c2 cell hypertrophy and explore its mechanism of action. The model of hypertrophy was induced by Ang Ⅱ(1×10-6 mol·L-1),and cardiomyocytes were incubated with different concentrations of AC. Western blot was used to quantify the protein expression levels of atrial natriuretic peptide(ANP),brain natriuretic peptide(BNP),β-myosin heavy chain(β-MHC),and α-smooth muscle actin(α-SMA). Real-time quantitative PCR(qRT-PCR) was used to quantify the mRNA expression levels of cardiac hypertrophic markers ANP,BNP and β-MHC. In addition,the fluorescence intensity of the F-actin marker,an important component of myofibrils,was detected by using laser confocal microscope. AC could significantly reverse the increase of total protein content in H9 c2 cells induced by Ang Ⅱ; qRT-PCR results showed that AC could significantly inhibit the ANP,BNP and β-MHC mRNA up-regulation induced by AngⅡ. Western blot results showed that AC could significantly inhibit the ANP,BNP and β-MHC protein up-regulation induced by AngⅡ. In addition,F-actin expression induced by Ang Ⅱ could be inhibited by AC,and multiple indicators of cardiomyocyte hypertrophy induced by Ang Ⅱ could be down-regulated,indicating that AC may inhibit cardiac hypertrophy by inhibiting the expression of hypertrophic factors,providing new clues for exploring the cardiovascular protection of AC.
Aconitine ; pharmacology ; Actins ; metabolism ; Angiotensin II ; Atrial Natriuretic Factor ; metabolism ; Cardiac Myosins ; metabolism ; Cardiomegaly ; Cells, Cultured ; Humans ; Hypertrophy ; Myocytes, Cardiac ; drug effects ; Myosin Heavy Chains ; metabolism ; Natriuretic Peptide, Brain ; metabolism

Neuropeptide Y (NPY) receptors are present in cardiac membranes. However, its physiological roles in the heart are not clear. The aim of this study was to define the direct effects of pancreatic polypeptide (PP) on atrial dynamics and atrial natriuretic peptide (ANP) release in perfused beating atria. Pancreatic polypeptides, a NPY Y4 receptor agonist, decreased atrial contractility but was not dose-dependent. The ANP release was stimulated by PP in a dose-dependent manner. GR 23118, a NPY Y4 receptor agonist, also increased the ANP release and the potency was greater than PP. In contrast, peptide YY (3-36) (PYY), an NPY Y2 receptor agonist, suppressed the release of ANP with positive inotropy. NPY, an agonist for Y1, 2, 5 receptor, did not cause any significant changes. The pretreatment of NPY (18-36), an antagonist for NPY Y3 receptor, markedly attenuated the stimulation of ANP release by PP but did not affect the suppression of ANP release by PYY. BIIE0246, an antagonist for NPY Y2 receptor, attenuated the suppression of ANP release by PYY. The responsiveness of atrial contractility to PP or PYY was not affected by either of the antagonists. These results suggest that NPY Y4 and Y2 receptor differently regulate the release of atrial ANP.
Animals ; Arginine/analogs & derivatives/pharmacology ; Atrial Natriuretic Factor/*metabolism ; Benzazepines/pharmacology ; Gene Expression Regulation ; Pancreatic Polypeptide/pharmacology ; Peptide YY/pharmacology ; Rats ; Rats, Sprague-Dawley ; Receptors, Neuropeptide Y/agonists/antagonists & inhibitors/*metabolism