Are the atrial natriuretic peptides a missing link predicting low-voltage areas in atrial fibrillation? Introducing the novel biomarker-based atrial fibrillation substrate prediction (ANP) score.

BACKGROUND: In patients with atrial fibrillation (AF), left atrial (LA) enlargement, and the presence of low-voltage areas (LVAs) indicate an advanced disease stage. NT-proANP is a biomarker, which is significantly higher in both phenotypes. Prediction of LVAs before catheter ablation could impact the prognosis and therapeutical management in AF patients. OBJECTIVE: The aim of this study was to (a) analyze the predictive value of a novel biomarker-based AF substrate prediction score, and (b) compare it with DR-FLASH and APPLE scores. METHODS: Patients undergoing first AF catheter ablation were included. LA volume (LAV) was analyzed prior to ablation using cardiovascular magnetic resonance imaging (CMR). Blood plasma samples from the femoral vein were collected before AF ablation. NT-proANP was analyzed using commercially available assays. LVAs were determined using high-density maps during catheter ablation and defined as <0.5 mV. The novel ANP score (one point for Age ≥ 65 years, NT-proANP > 17 ng/mL, and Persistent AF) was calculated at baseline. RESULTS: The study population included 156 AF patients (64 ± 10 years, 65% males, 61% persistent AF, 28% LVAs). The cut-off ANP score ≥ 2 demonstrated 77% sensitivity and 70% specificity. On logistic regression (odds ratio [OR] 3.469) and receiver operating characteristic (ROC) analysis (area under the curve [AUC] 0.778, P < .001), the ANP score significantly predicted LVAs presence. There were no differences between novel ANP score - which is a new one - is described in the Abstract; with APPLE (AUC 0.718, P = .378) and DR-FLASH (AUC 0.766, P = .856) scores. CONCLUSIONS: The novel biomarker-based ANP score demonstrates good prediction of LVAs.

Association Between Cardiovascular Magnetic Resonance-Derived Left Atrial Dimensions, Electroanatomical Substrate and NT-proANP Levels in Atrial Fibrillation.

Background Enlargement of left atrial ( LA ) size indicates advanced disease stage in patients with atrial fibrillation ( AF ) and is associated with poor success of different AF therapies. Two dimensional echocardiographic LA measurements do not reliably reflect the true size of LA anatomy. The aim of the current study was: 1) to analyze cardiovascular magnetic resonance ( CMR )-derived LA dimensions and their association with low voltage areas ( LVA ); and 2) to investigate the association between these parameters and NT -pro ANP (N-terminal proatrial natriuretic peptide) levels. Methods and Results Patients undergoing first AF catheter ablation were included. All patients underwent CMR imaging (Ingenia 1.5T Philips) before intervention. CMR data ( LA volume, superior-inferior, transversal and anterior-posterior LA diameters) were measured in all patients. LVA were determined using high-density maps and a low voltage threshold <0.5 mV. Blood plasma samples from femoral vein were collected before catheter ablation. NT -pro ANP levels were studied using commercially available assays. There were 216 patients (65±11 years, 59% males, 56% persistent AF , 26% LVA ) included into analyses. NT -pro ANP levels in patients with LVA were significantly higher than in those without (median/interquartile range 22 [13-29] versus 15 [9-22] pg/mL, P=0.004). All CMR derived LA diameters correlated significantly with persistent AF ( r²=0.291-0.468, all P<0.001), LVA ( r²=0.187-0.306, all P<0.001), and NT -pro ANP levels ( r²=0.258-0.352, P<0.01). On logistic regression multivariable analysis, age (odds ratio=1.090, 95% confidence interval: 1.030-1.153, P=0.003), females (odds ratio=2.686, 95% confidence interval: 1.047-6.891, P=0.040), and LA volume (odds ratio=1.022, 95% confidence interval: 1.009-1.035, P=0.001) remained significant predictors for LVA . Conclusions Left atrial CMR parameters are associated with persistent AF , low voltage areas and NT -pro ANP levels. LA volume is the most significant predictor for LVA .

Role of the heart in blood pressure lowering during chronic baroreflex activation: insight from an in silico analysis.

Electrical stimulation of the baroreflex chronically suppresses sympathetic activity and arterial pressure and is currently being evaluated for the treatment of resistant hypertension. The antihypertensive effects of baroreflex activation are often attributed to renal sympathoinhibition. However, baroreflex activation also decreases heart rate, and robust blood pressure lowering occurs even after renal denervation. Because controlling renal sympathetic nerve activity (RSNA) and cardiac autonomic activity cannot be achieved experimentally, we used an established mathematical model of human physiology (HumMod) to provide mechanistic insights into their relative and combined contributions to the cardiovascular responses during baroreflex activation. Three-week responses to baroreflex activation closely mimicked experimental observations in dogs including decreases in blood pressure, heart rate, and plasma norepinephrine and increases in plasma atrial natriuretic peptide (ANP), providing validation of the model. Simulations showed that baroreflex-induced alterations in cardiac sympathetic and parasympathetic activity lead to a sustained depression of cardiac function and increased secretion of ANP. Increased ANP and suppression of RSNA both enhanced renal excretory function and accounted for most of the chronic blood pressure lowering during baroreflex activation. However, when suppression of RSNA was blocked, the blood pressure response to baroreflex activation was not appreciably impaired due to inordinate fluid accumulation and further increases in atrial pressure and ANP secretion. These simulations provide a mechanistic understanding of experimental and clinical observations showing that baroreflex activation effectively lowers blood pressure in subjects with previous renal denervation. NEW & NOTEWORTHY Both experimental and clinical studies have shown that the presence of renal nerves is not an obligate requirement for sustained reductions in blood pressure during chronic electrical stimulation of the carotid baroreflex. Simulations using HumMod, a mathematical model of integrative human physiology, indicated that both increased secretion of atrial natriuretic peptide and suppressed renal sympathetic nerve activity play key roles in mediating long-term reductions in blood pressure during chronic baroreflex activation.

[Effects of acupuncture on ANP and CNP in adrenal gland and CORT in plasma in rats with chronic emotional stress anxiety].

OBJECTIVE: To analyze the effects of acupuncture on the level of atrial natriuretic peptide (ANP), C-type natriuretic peptide (CNP) in adrenal gland and the content of corticosterone (CORT) in plasma in rats withchronic emotional stress anxiety, and to explore the partial action mechanism of acupuncture on anxiety disorder. METHODS: Thirty-two healthy Sprague-Dawley (SD) rats, after 7 days of feeding and domestication, were randomly divided into a blank group (10 rats), a model group (11 rats) and an acupuncture group (11 rats). The rats inthe model group and acupuncture group were treated with unpredictable chronic emotional stress (CES) method toestablish the model of anxiety. Rats in the acupuncture group were treated with acupuncture at "Neiguan" (PC 6)and "Shenmen" (HT 7), once every other day, 30 minutes each time. The model establishment and treatment lasted 15 days. Rats in the blank group were treated with identical immobilization but no treatment was given. Theelevated plus maze was used to test the behavioral changes of rats with anxiety; the level of CORT in plasma wasdetected by ELISA, and the expression level of CNP and ANP in adrenal cortex and medulla was detected by immunohistochemical method. RESULTS: (1) The percentage of open-arms time in total time (OT%) in elevated plus maze in the model group was significantly lower than that in the blank group (P<0. 05); the OT% in the acupuncture group was significantly higher than that in the model group (P<0.01). (2) The content of CORT in plasma in the model group was higher than that in the blank group (P<0. 05), while that in the acupuncture group was significantly lower than that in the model group (P<0. 05). (3) The expression of ANP in adrenal medulla and cortex in the model group was lower than that in the blank group (P<0. 01), while the expression of CNP in adrenal medulla and cortex in the model group was higher than that in the blank group (P<0. 01). CONCLUSION: The effects of acupuncture against anxiety are likely to be related to the regulation on the expression of ANP and CNP in adrenal medulla, affecting the release of CORT and inhibition on the activity !f hypothalamic-pituitary-adrenal axis (HPA axis).

Associations of serum n-3 and n-6 polyunsaturated fatty acids with plasma natriuretic peptides.

BACKGROUND/OBJECTIVES: The n-3 and n-6 polyunsaturated fatty acids (PUFAs) have been associated with lower risk of cardiovascular disease (CVD), but little is known about their association with natriuretic peptides (NPs), a marker for CVD risk. The aim of this study was to investigate the association of serum n-3 and n-6 PUFAs with NPs. SUBJECTS/METHODS: A cross-sectional analysis of the association between serum n-3 and n-6 PUFAs with plasma N-terminal atrial (NT-proANP) and brain (NT-proBNP) NPs in a population-based sample of 985 men aged 46-65 years from Eastern Finland. RESULTS: After adjustment for age and examination year, only serum n-6 PUFA arachidonic acid (ARA) was inversely associated with NT-proANP (P-trend across quartiles=0.02), but further adjustments for conventional risk factors (body mass index, smoking, alcohol intake, systolic blood pressure, low-density lipoprotein cholesterol and history of CVD) attenuated the association (P-trend=0.10). The associations with the other PUFAs were not statistically significant. Among the PUFAs, only serum n-3 PUFA docosapentaenoic acid (DPA; P-trend=0.03) and ARA (P-trend=0.02) had inverse associations with NT-proBNP after adjustment for age and examination years. The associations were again attenuated after further adjustments but remained statistically significant for DPA (P-trend=0.05). Our results also suggested that the inverse associations may be more evident among those using beta-blockers. CONCLUSIONS: Our study suggests little overall impact of serum n-3 or n-6 PUFAs on plasma NPs.

Terminalia arjuna bark extract improves diuresis and attenuates acute hypobaric hypoxia induced cerebral vascular leakage.

ETHNOPHARMACOLOGICAL RELEVANCE: Terminalia arjuna (Roxb. ex DC.) Wight & Arn. (T. arjuna) has been widely used in the traditional ayurvedic system of medicine as a cardioprotectant and for acute and chronic renal diseases supporting its ethnopharmacological use. AIM OF THE STUDY: The present study aimed at evaluating the diuretic action of an alcoholic extract of T. arjuna and its possible use as a prophylactic to prevent vascular leakage during acute mountain sickness at high altitude. MATERIALS AND METHODS: Rats were exposed to hypobaric hypoxia simulated to an altitude of 27,000 ft. in a decompression chamber for 12h. T. arjuna bark extract was administered at a single dose of 150 mg/kg (p.o.) to male Sprague Dawley rats (200 ± 20 g) 30 min prior to exposure. Total urine volume was measured during exposure to hypobaric hypoxia. The animals were then investigated for cerebral vascular leakage and serum concentration of sodium, potassium, renin, angiotensin-II, aldosterone and atrial natriuretic peptide (ANP). RESULTS: T. arjuna ameliorated acute hypobaric hypoxia induced decrease in glomerular filtration rate (p<0.5), increased total urine output (p<0.5) and prevented cerebral vascular leakage in hypoxic rats. T. arjuna treated animals also showed decrease in serum levels of renin (p<0.001) and angiotensin-II (p<0.5) as compared to placebo treated animals. Administration of T. arjuna attenuated acute hypobaric hypoxia induced oxidative stress, improved aldosterone levels and altered electrolyte balance in animals through ANP dependent mechanism. CONCLUSION: Results of the present study indicate towards diuretic potential of hydro-alcoholic extract of T. arjuna bark and provide evidence for its novel application as a prophylactic to attenuate acute hypobaric hypoxia induced cerebral vascular leakage through ANP mediated modulation of renin-angiotensin-aldosterone system.

[Effects of Electroacupuncture Stimulation of "Neiguan" (PC 6) at Different Frequencies on Plasma Vasoactive Substance Levels in Myocardial Ischemic Reperfusion Rats].

OBJECTIVE: To observe the effect of electroacupuncture (EA) stimulation of "Neiguan" (PC 6) at different frequencies on plasma vasoactive substance levels in myocardial ischemia-reperfusion (MIR) injury rats, so as to explore its mechanisms underlying improvement of acute myocardial ischemia. METHODS: A total of 40 Wistar rats were randomized into control, model, high frequency (HF, 120 Hz) and low frequency (LF, 20 Hz) groups (n = 10 in each group). The MIR model was established by occlusion of the anterior descending branch (ADB) of the left coronary artery for 30 min, followed by reperfusion for 40 min. EA (3 V, 120 Hz or 20 Hz) was applied to bilateral "Neiguan" (PC 6) for 50 min immediately after occlusion of ADB. Subsequently, the contents of plasma endothelin (ET), atrial natriuretic peptide (ANP), thromboxane B 2 (TXB2) and 6-Keto-PGF1, were assayed by radioimmunoassay, and the content of serum nitric oxide (NO) was detected by nitrate reductase method. RESULTS: Compared with the control group, the contents of plasma ET, ANP and TXB2 in the model group were significantly increased (P < 0.05), and that of plasma 6-Keto-PGF1α in the model group was notably decreased (P < 0.05), but no significant change was found in serum NO level (P > 0.05). Compared with the model group, the contents of plasma ET, ANP and TXB2 were considerably decreased, and plasma 6-Keto-PGF1α and serum NO contents were obviously increased in both HF and LF groups (P < 0.05). No significant differences were found between the HF and LF groups in plasma ET , ANP, TXB2 and 6-Keto-PGF1α contents (P > 0.05), but the HF EA was markedly superior to the LF EA in up-regulating the content of serum NO (P < 0.05). CONCLUSION: EA stimulation of "Neiguan" (PC 6) can down-regulate the contents of plasma ET, ANP and TXB2 and up-regulate contents of plasma 6-Keto-PGF1α and serum NO in MIR rats, which may contribute to its effect in relieving acute ischemic myocardial injury. The effect of HF EA is better than LF EA in raising blood NO level.

Yogurt Containing the Probacteria Lactobacillus acidophilus Combined with Natural Antioxidants Mitigates Doxorubicin-Induced Cardiomyopathy in Rats.

Probiotics and antioxidants have a definite improving effect in cardiovascular diseases. This study aims at mitigating doxorubicin toxicity on cardiac function through consuming a functional food. Five groups of adult male Sprague-Dawley rats were used along 22 weeks. Group I received 30 g/kg/day food enriched with yogurt, green tea extract, and carrots (80, 0.84, and 100 g/kg diet, respectively) from the first week, group II received carvedilol 30 mg/kg/day orally from week 17, group III received both carvedilol and tested food, and groups IV and V were +ve and -ve control groups, respectively. In week 17, cardiomyopathy was induced by i.p. injection of 2.5 mg/kg doxorubicin every 48 h for 2 weeks. Histopathological and electrophysiological examinations and biochemical analysis were done. Lipid peroxidation, antioxidant effect, heart failure compensatory mediators, and proinflammatory cytokines were assessed. Tested food normalized time between the start of Q wave and the end of T wave on electrocardiogram (QT interval) and heart rate compared to the doxorubicin group (P<.05). It also improved hypertrophy indicated by a significant (P<.05) decrease in heart/body weight ratio, angiotensin-II (Ang-II), and atrial natriuretic peptide (ANP) serum levels. Histopathological examination of cardiac sections from the tested food group revealed less marked vacuolization and low perivascular fibrosis percentage (0.7803 ± 0.04). A significant (P<.001) decrease in serum creatine kinase-membrane bound, lactate dehydrogenase, triglycerides, cholesterol, low-density lipoprotein cholesterol, and tissue malondialdehyde (MDA) levels was observed in addition to an increase in serum Na(+)/K(+) ATP1A1 and cardiac reduced glutathione (GSH) levels. Tested food also lowered the inflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) serum levels significantly (P<.01). Probiotic food containing Lactobacillus acidophilus, green tea, and carrots can improve membrane integrity and cardiac contractility in doxorubicin-induced cardiomyopathy by decreasing TNF-α, IL-6, MDA, increasing GSH, and modulating compensatory mediators such as Ang-II and ANP.

Does continuous endurance exercise in water elicit a higher release of ANP and BNP and a higher plasma concentration of FFAs in pre-obese and obese men than high intensity intermittent endurance exercise? - study protocol for a randomized controlled trial.

BACKGROUND: Atrial natriuretic peptides (ANP) and Brain natriuretic peptides (BNP) stimulate fat cell plasma membrane receptors. They are potent lipolytic agents on isolated fat cells from subcutaneous adipose tissue. The physiological effects of continuous endurance exercise on ANP release and plasma free fatty acids (FFA) concentrations have been well described. The enhancement of fat metabolism using high intensity intermittent exercise protocols has been assessed in more recent investigations. The combined effects of endurance exercise and water immersion on ANP and FFA plasma concentration and the magnitude of excess post-exercise oxygen consumption (EPOC) might be further enhanced by choosing the most effective exercise protocol. Exercise modalities may play a significant role in the future prevention and treatment of obesity. METHODS/DESIGN: The two testing trials will be performed according to a randomized and cross-over design. Twenty healthy sedentary pre-obese and obese class-1 men will be scrutinized with regard to their metabolic responses to continuous exercise in water and to high intensity endurance exercise in water. Both trials will be matched for energy expenditure. After preliminary testing, the tests will be conducted as repeated measurements. The two different exercise protocols will be compared. The aims of the study are to investigate (1) whether continuous endurance exercise or high intensity intermittent endurance exercise in water elicits both a higher release of ANP and BNP and a higher plasma concentration of glycerol and (2) to determine whether continuous endurance exercise in water or a high intensity intermittent endurance exercise in water would lead to a more pronounced short term (two hours) EPOC effect. DISCUSSION: If our hypothesis would be confirmed, the most effective exercise protocol based on the combined effects of high intensity endurance exercise and water immersion on ANP and BNP release and glycerol plasma concentrations can be identified. Moreover, the magnitude of the EPOC effect can be augmented. Our study would provide a major contribution for creating optimized exercise modalities in the prevention and treatment of obesity. TRIAL REGISTRATION: Current controlled trials, ISRCTN95488515.

Inhibition of cyclooxygenase-2 reduces hypothalamic excitation in rats with adriamycin-induced heart failure.

BACKGROUND: The paraventricular nucleus (PVN) of the hypothalamus plays an important role in the progression of heart failure (HF). We investigated whether cyclooxygenase-2 (COX-2) inhibition in the PVN attenuates the activities of sympathetic nervous system (SNS) and renin-angiotensin system (RAS) in rats with adriamycin-induced heart failure. METHODOLOGY/PRINCIPAL FINDING: Heart failure was induced by intraperitoneal injection of adriamycin over a period of 2 weeks (cumulative dose of 15 mg/kg). On day 19, rats received intragastric administration daily with either COX-2 inhibitor celecoxib (CLB) or normal saline. Treatment with CLB reduced mortality and attenuated both myocardial atrophy and pulmonary congestion in HF rats. Compared with the HF rats, ventricle to body weight (VW/BW) and lung to body weight (LW/BW) ratios, heart rate (HR), left ventricular end-diastolic pressure (LVEDP), left ventricular peak systolic pressure (LVPSP) and maximum rate of change in left ventricular pressure (LV±dp/dtmax) were improved in HF+CLB rats. Angiotensin II (ANG II), norepinephrine (NE), COX-2 and glutamate (Glu) in the PVN were increased in HF rats. HF rats had higher levels of ANG II and NE in plasma, higher level of ANG II in myocardium, and lower levels of ANP in plasma and myocardium. Treatment with CLB attenuated these HF-induced changes. HF rats had more COX-2-positive neurons and more corticotropin releasing hormone (CRH) positive neurons in the PVN than did control rats. Treatment with CLB decreased COX-2-positive neurons and CRH positive neurons in the PVN of HF rats. CONCLUSIONS: These results suggest that PVN COX-2 may be an intermediary step for PVN neuronal activation and excitatory neurotransmitter release, which further contributes to sympathoexcitation and RAS activation in adriamycin-induced heart failure. Treatment with COX-2 inhibitor attenuates sympathoexcitation and RAS activation in adriamycin-induced heart failure.

Thirst deficits in aged rats are reversed by dietary omega-3 fatty acid supplementation.

During heat waves many elderly individuals die as a consequence of dehydration. This is partially due to deficits in mechanisms controlling thirst. Reduced thirst following dipsogenic stimuli is well documented in aged humans and rodents. Low in vivo long-chain omega-3 fatty acid levels, as can occur in aging, have been shown to alter body fluid and sodium homeostasis. Therefore, the effect of dietary omega-3 fatty acid supplementation on drinking responses in aged rats was examined. Omega-3 fatty acids reversed thirst deficits in aged rats following dehydration and hypertonic stimuli; angiotensin (ANG) II induced drinking was unaffected in aged rats. Plasma atrial natriuretic peptide (ANP) and arginine vasopressin (AVP) were altered with age, but not affected by diet. Aged omega-3 fatty acid deficient animals displayed increased hypothalamic cytosolic phospholipase A(2) (cPLA(2)), cyclooxygenase (COX)-2, and prostaglandin E (PGE) synthase messenger (m)RNA expression, compared with animals that received omega-3 fatty acids. The aged low omega-3 fatty acid fed animals had significantly elevated hypothalamic PGE(2) compared with all other groups. Hypothalamic PGE(2) was negatively correlated with drinking induced by both dehydration and hypertonicity. The results indicate that PGE(2) may be the underlying mechanism of the reduced thirst observed in aging.

Diets rich in saturated fat and/or salt differentially modulate atrial natriuretic peptide and renin expression in C57BL/6 mice.

PURPOSE: To study the effects of a diet rich in salt and/or saturated fat on atrial natriuretic peptide (ANP)-granules, hypertension, renin expression, and cardiac structure in C57Bl/6 mice. METHODS: Young adult male mice were separated into four groups (n = 12) and fed one of the following for 9 weeks: standard chow/normal salt (SC-NS), high-fat chow/normal salt (HF-NS), standard chow/high salt (SC-HS) and high-fat chow/high salt (HF-HS). Alterations in the serum ANP, ultrastructural analysis of cardiomyocytes that produce ANP, structural analysis of the left ventricle, blood pressure, renin expression, glomerular filtration rate (GFR), feed efficiency, and lipid and glucose parameters were examined. RESULTS: The HF-NS diet showed a small increase in ANP production and left ventricular hypertrophy, increased food efficiency, and abnormal lipid and glucose parameters. The SC-HS diet showed a large increase in ANP granules in myocytes and corresponding elevation in ANP serum levels, left ventricular hypertrophy, hypertension, decrease in renin levels, and increase in GFR. The combination of the two diets (HF-HS) had an additive effect. CONCLUSION: The incorporation of a high-fat high-salt diet induced ultrastructural changes in cardiomyocytes, increased the production of ANP and increased its serum level, and reduced the amount of renin in the kidney.

Effect of potassium supplementation on renal tubular function, ambulatory blood pressure and pulse wave velocity in healthy humans.

BACKGROUND: Potassium is the main intracellular cation, which contributes to keeping the intracellular membrane potential slightly negative and elicits contraction of smooth, skeletal and cardiac muscle. A change in potassium intake modifies both cardiovascular and renal tubular function. The purpose of the trial was to investigate the effect of dietary potassium supplementation, 100 mmol daily in a randomized, placebo-controlled, crossover trial of healthy participants during two periods of 28 days duration. The participants (N = 21) received a diet that was standardized regarding energy requirement, and sodium and water intake. METHODS: 24-hour ambulatory blood pressure (ABP) and applanation tonometry were used to assess blood pressure, pulse wave velocity (PWV), augmentation index (AIx) and central blood pressure (CBP). Immunoassays were used for measurements of plasma concentrations of vasoactive hormones: renin (PRC), angiotensin II (Ang II), aldosterone (Aldo), atrial natriuretic peptide (ANP), vasopressin (AVP), pro-brain natriuretic peptide (pro-BNP),endothelin (Endo), urinary excretions of aquaporin 2 (AQP2), cyclic AMP (cAMP), and the ß-fraction of the epithelial sodium channel (ENaC(ß)). RESULTS: AQP2 excretion increased during potassium supplementation, and free water clearance fell. The changes in urinary potassium excretion and urinary AQP2 excretion were significantly and positively correlated. Aldo increased. GFR, u-ENaC- ß, PRC, Ang II, ANP, BNP, Endo, blood pressure and AI were not significantly changed by potassium supplementation, whereas PWV increased slightly. CONCLUSIONS: Potassium supplementation changed renal tubular function and increased water absorption in the distal part of the nephron. In spite of an increase in aldosterone in plasma, blood pressure remained unchanged after potassium supplementation.

Haemodynamic, endocrine and renal actions of adrenomedullin 5 in an ovine model of heart failure.

AM5 (adrenomedullin 5), a newly described member of the CGRP (calcitonin gene-related peptide) family, is reported to play a role in normal cardiovascular physiology. The effects of AM5 in HF (heart failure), however, have not been investigated. In the present study, we intravenously infused two incremental doses of AM5 (10 and 100 ng/min per kg of body weight each for 90 min) into eight sheep with pacing-induced HF. Compared with time-matched vehicle control infusions, AM5 produced progressive and dose-dependent increases in left ventricular dP/dt(max) [LD (low dose), +56 mmHg/s and HD (high dose), +152 mmHg/s] and cardiac output (+0.83 l/min and +1.81 l/min), together with decrements in calculated total peripheral resistance (-9.4 mmHg/min per litre and -14.7 mmHg/min per litre), mean arterial pressure (-2.8 mmHg and -8.4 mmHg) and LAP (left atrial pressure; -2.6 mmHg and -5.6 mmHg) (all P<0.001). HD AM5 significantly raised PRA (plasma renin activity) (3.5-fold increment, P<0.001), whereas plasma aldosterone levels were unchanged over the intra-infusion period and actually fell in the post-infusion period (70% decrement, P<0.01), resulting in a marked decrease in the aldosterone/PRA ratio (P<0.01). Despite falls in LAP, plasma atrial natriuretic peptide and B-type natriuretic peptide concentrations were maintained relative to controls. AM5 infusion also induced significant increases in urine volume (HD 2-fold increment, P<0.05) and urine sodium (2.7-fold increment, P<0.01), potassium (1.7-fold increment, P<0.05) and creatinine (1.4-fold increment, P<0.05) excretion and creatinine clearance (60% increment, P<0.05). In conclusion, AM5 has significant haemodynamic, endocrine and renal actions in experimental HF likely to be protective and compensatory in this setting. These results suggest that AM5 may have potential as a therapeutic agent in human HF.

[Effect of qianyang recipe on correlated indices of hypertension rats of gan-yang hyperactivity syndrome].

OBJECTIVE: To study the effect of Qianyang Recipe (QYR) on the Gan-yang hyperactivity syndrome (GYHS), the blood pressure, and correlated vascular regulatory factors of hypertension rat. METHODS: Thirty SD rats were randomly divided into the normal control group, the model group, and the QYR group, ten in each. Hypertension rat model of GYHS was prepared using Aconiti Praeparata Decoction plus ephedrine plus salt water. Rats in the QYR group orally took QYR physic liquor, while distilled water was given to rats in the normal control group and the model group. They were medicated for 28 successive days. The facial temperature, the grip strength, and the systolic pressure were determined once every 7 days. Rats' irritable degree and feather color were observed and recorded once every 14 days. After the last administration the plasma renin (PR), angiotensin II (Ang II), aldosterone (ALD), atrial natriuretic peptide (ANP), calcitonin gene-related peptide (cGRP) were determined. RESULTS: Compared with the model group of the same phase, the facial temperature of rats in the QYR group significantly decreased on the 14th, 21th and 28th day after administration. The systolic pressure obviously decreased on the 21st day after administration. On the 28th day after administration symptoms such as irritability, dry hair were improved, and the Ang II level decreased. There was significant difference in all these changes (P<0.05, P<0.01). CONCLUSIONS: QYR could relieve GYHS rats' symptoms such as facial hotness, irritability, dry hair, and so on, and decrease the systolic pressure. Decreased Ang II level might be one of its mechanisms.

An initial characterization of N-terminal-proatrial natriuretic peptide in serum of Sprague Dawley rats.

In the clinical setting, natriuretic peptides (NPs) have proven to be reliable noninvasive markers for diagnostic, prognostic, and therapeutic monitoring of heart failure. Given their proven utility in humans, NPs are potential candidates for translational biomarkers during drug development to detect drug-induced hemodynamic stress resulting in cardiac hypertrophy in preclinical species. We evaluated the intra- and interassay precision and the stability of serum N-terminal-proatrial natriuretic peptide (NT-proANP) using a commercially available enzyme-linked immunoassay (EIA). We then measured NT-proANP concentrations in 532 serum samples from 337 male Crl:CD(SD) rats with or without pressure-induced cardiac hypertrophy. Additionally, we established a reference range using samples from control animals across multiple studies. The data demonstrate that the NT-proANP EIA is a robust and reproducible assay for the measurement of NT-proANP. The noninvasive translational utility, minimal sample volume requirement, and the lack of existing hypertrophic biomarkers in the male rat make NT-proANP an excellent candidate for further interrogation as a biomarker of cardiac hypertrophy in preclinical toxicology investigations.

Inhibition of dehydration-induced water intake by glucocorticoids is associated with activation of hypothalamic natriuretic peptide receptor-A in rat.

Atrial natriuretic peptide (ANP) provides a potent defense mechanism against volume overload in mammals. Its primary receptor, natriuretic peptide receptor-A (NPR-A), is localized mostly in the kidney, but also is found in hypothalamic areas involved in body fluid volume regulation. Acute glucocorticoid administration produces potent diuresis and natriuresis, possibly by acting in the renal natriuretic peptide system. However, chronic glucocorticoid administration attenuates renal water and sodium excretion. The precise mechanism underlying this paradoxical phenomenon is unclear. We assume that chronic glucocorticoid administration may activate natriuretic peptide system in hypothalamus, and cause volume depletion by inhibiting dehydration-induced water intake. Volume depletion, in turn, compromises renal water excretion. To test this postulation, we determined the effect of dexamethasone on dehydration-induced water intake and assessed the expression of NPR-A in the hypothalamus. The rats were deprived of water for 24 hours to have dehydrated status. Prior to free access to water, the water-deprived rats were pretreated with dexamethasone or vehicle. Urinary volume and water intake were monitored. We found that dexamethasone pretreatment not only produced potent diuresis, but dramatically inhibited the dehydration-induced water intake. Western blotting analysis showed the expression of NPR-A in the hypothalamus was dramatically upregulated by dexamethasone. Consequently, cyclic guanosine monophosphate (the second messenger for the ANP) content in the hypothalamus was remarkably increased. The inhibitory effect of dexamethasone on water intake presented in a time- and dose-dependent manner, which emerged at least after 18-hour dexamethasone pretreatment. This effect was glucocorticoid receptor (GR) mediated and was abolished by GR antagonist RU486. These results indicated a possible physiologic role for glucocorticoids in the hypothalamic control of water intake and revealed that the glucocorticoids can act centrally, as well as peripherally, to assist in the normalization of extracellular fluid volume.

[Dynamic study on inhibition of qi-benefiting, blood-activating recipe on myocardial hypertrophy induced by ISO in rats].

OBJECTIVE: To observe the effect of Qi-Benefiting, Blood-Activating Recipe on the different pathologic stage of myocardial hypertrophy induced by ISO in rats. METHODS: Myocardial hypertrophy rats were induced by isoproterenol, and treated with Qi-Benefiting, Blood-Activating Recipe for 5,10 and 15 weeks, hemodynamic parameters, LVMI, HMI were determined, ANP and BNP were analysed. RESULTS: Qi-Benefiting, Blood-Activating Recipe could increase cardiac output and improve hemodynamic parameters all after 5, 10 and 15 weeks' treatment (P<0.05). It could decrease the contents of ANP and BNP after 5, 10 and 15 weeks' treatment (P<0.05). Qi-Benefiting, Blood-Activating Recipe could significantly decrease the levels of HWI and LVMI after 5, 10 and 15 weeks' treatment (P<0.05). CONCLUSION: Qi-Benefiting, Blood-Activating Recipe can significant improve hemodynamic status, increase cardiac output and decrease the level of neurohormonal factors.

Erythropoietin protects from reperfusion-induced myocardial injury by enhancing coronary endothelial nitric oxide production.

OBJECTIVE: Cardioprotective properties of recombinant human Erythropoietin (rhEpo) have been shown in in vivo regional or ex vivo global models of ischemia-reperfusion (I/R) injury. The aim of this study was to characterize the cardioprotective potential of rhEPO in an in vivo experimental model of global I/R approximating the clinical cardiac surgical setting and to gain insights into the myocardial binding sites of rhEpo and the mechanism involved in its cardioprotective effect. METHODS: Hearts of donor Lewis rats were arrested with cold crystalloid cardioplegia and after 45 min of cold global ischemia grafted heterotopically into the abdomen of recipient Lewis rats. Recipients were randomly assigned to control non-treated or Epo-treated group receiving 5000 U/kg of rhEpo intravenously 20 min prior to reperfusion. At 5 time points 5-1440 min after reperfusion, the recipients (n=6-8 at each point) were sacrificed, blood and native and grafted hearts harvested for subsequent analysis. RESULTS: Treatment with rhEpo resulted in a significant reduction in myocardial I/R injury (plasma troponin T) in correlation with preservation of the myocardial redox state (reduced glutathione). The extent of apoptosis (activity of caspase 3 and caspase 9, TUNEL test) in our model was very modest and not significantly affected by rhEpo. Immunostaining of the heart tissue with anti-Epo antibodies showed an exclusive binding of rhEpo to the coronary endothelium with no binding of rhEpo to cardiomyocytes. Administration of rhEpo resulted in a significant increase in nitric oxide (NO) production assessed by plasma nitrite levels. Immunostaining of heart tissue with anti-phospho-eNOS antibodies showed that after binding to the coronary endothelium, rhEpo increased the phosphorylation and thus activation of endothelial nitric oxide synthase (eNOS) in coronary vessels. There was no activation of eNOS in cardiomyocytes. CONCLUSIONS: Intravenous administration of rhEpo protects the heart against cold global I/R. Apoptosis does not seem to play a major role in the process of tissue injury in this model. After binding to the coronary endothelium, rhEpo enhances NO production by phosphorylation and thus activation of eNOS in coronary vessels. Our results suggest that cardioprotective properties of rhEpo are at least partially mediated by NO released by the coronary endothelium.