Effects of incremental infusions of atrial natriuretic factor on aldosterone, renin, and blood pressure in humans

Enhanced heart failure, mortality and renin activation in female mice with experimental dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is the major cause of heart failure affecting both women and men. Limited clinical studies show conflicting data in sex-related differences in the progression of dilated cardiomyopathy and heart failure (HF) outcomes. We examined the comparative sex-related progression of cardiomyopathy and the development of HF (at 4, 7, 13 weeks of age) in a well-established, transgenic mouse model of DCM that recapitulates the progressive stages of human HF. By 13 weeks of age, female mice with DCM had more severe left ventricular systolic dysfunction, left ventricular dilation and wall thinning (P<0.001 for all) than age-matched male mice with DCM. Female mice also had greater lung edema (P<0.001), cardiac fibrosis (P<0.01) and pleural effusions, which were not rescued by ovariectomy. By comparison to DCM male mice at 13 weeks, these pathological changes in female mice with DCM, were associated with significant increases in plasma active renin (P<0.01), angiotensin II (P<0.01) and aldosterone levels (P<0.001). In comparison to DCM male mice, DCM female mice also showed differential expression of the natriuretic peptide system with lower corin and higher ANP, BNP and cGMP levels at 13 weeks of age. We conclude, that female mice with experimental DCM have an accelerated progression of cardiomyopathy and HF, which was not corrected by early ovariectomy. These alterations are associated with early renin activation with increased angiotensin II and aldosterone levels, and altered expression of the natriuretic peptide system.

Adaptation of Renal Function in Heart Failure

Congestive heart failure is the only major cardiovascular disease with an increasing incidence and prevalence in industrialized countries. Despite considerable progress in the clinical management of heart failure during the last 20 years, the prognosis is still worse than in many common types of cancer. The kidney is the main organ affected when cardiac function is compromised. In addition, the kidney significantly contributes to the development of the clinical syndrome of heart failure. Specific hemodynamic and neurohormonal abnormalities define the pathophysiology, clinical presentation, and prognosis of this disorder. In this setting, the kidney plays a dual role: the activation of the renin-angiotensin-aldosterone system and the regulation of sodium and water excretion. The kidney is generally intact in heart failure, but extrarenal stimuli alter its function to a point where mechanisms that are initially homeostatic become maladaptive. In this review article, the mechanisms involved in renal adaptation to heart failure are presented.

Influence of atrial natriuretic peptide, brain natriuretic peptide and urodilatin on the histamine-induced bronchoconstriction in the conscious guinea pig

The influence of human atrial natriuretic peptide (ANP) and of two related peptides, human brain natriuretic peptide (BNP) and urodilatin (URO) on the bronchoconstriction induced by inhalation of histamine in conscious, non-anaesthetized guinea pigs was tested.Changes in lung function were registered using two independent methods, one operating in a closed body-plethysmographic system, the other in an open system based on the time lag of air flow curves. The peptides were infused (0.25 ml/min) into the jugular vein for a period from 10 min before until 15 min after the histamine inhalation.ANP displayed virtually no effect on the bronchoconstriction. URO showed some inibition at 1280ng kg(-1) min(-1), but not at lower doses. BNP (640ng kg(-1) min(-1)) inhibited the bronchoconstriction markedly for the total registration period.It can be concluded from these results that BNP exerts bronchoprotective effects in the conscious guinea pig, which are superior to those of ANP or URO.

Acute decompensated heart failure: pathophysiology and treatment

Acute decompensated heart failure (ADHF) is an important milestone in the clinical course of heart failure (HF). It is an event associated with a significant deterioration in the prognosis of HF. Despite the progress that has been made in the development of new pharmacologic and nonpharmacologic therapy for HF, there is surprisingly limited advancement in the treatment of acute HF. There are currently no guidelines for the treatment of ADHF. This is a review of the current diagnostic evaluation and treatment of patients with ADHF.

Cloning and characterisation of natriuretic peptides from the venom glands of Australian elapids

The venom from Australian elapid snakes contains a complex mixture of polypeptide toxins that adversely affect multiple homeostatic systems within their prey in a highly specific and targeted manner. Included in these toxin families are the recently described venom natriuretic peptides, which display similar structure and vasoactive functions to mammalian natriuretic peptides. This paper describes the identification and detailed comparative analysis of the cDNA transcripts coding for the mature natriuretic peptide from a total of nine Australian elapid snake species. Multiple isoforms were identified in a number of species and represent the first description of a natriuretic peptide from the venom gland for most of these snakes. Two distinct natriuretic peptide isoforms were selected from the common brown snake (Pseudonaja textilis), PtNP-a, and the mulga (Pseudechis australis), PaNP-c, for recombinant protein expression and functional analysis. Only one of these peptides, PtNP-a, displayed cGMP stimulation indicative of normal natriuretic peptide activity. Interestingly, both recombinant peptides demonstrated a dose-dependent inhibition of angiotensin converting enzyme (ACE) activity, which is predictive of the vasoactive effects of the toxin. The natriuretic peptides, however, did not possess any coagulopathic activity, nor did they inhibit or potentiate thrombin, adenosine diphosphate or arachidonic acid induced platelet aggregation. The data presented in this study represent a significant resource for understanding the role of various natriuretic peptides isoforms during the envenomation process by Australian elapid snakes.

Association between human atrial natriuretic peptide Val7Met polymorphism and baseline blood pressure, plasma trough irbesartan concentrations, and the antihypertensive efficacy of irbesartan in rural Chinese patients with essential hypertension

BACKGROUND

Individual variations in the pharmacokinetics and pharmacodynamics of antihypertensive drugs are influenced by genetic and environmental factors. The ANP gene, which encodes the precursor of atrial natriuretic peptide (ANP), is among the candidate genes for genetic susceptibility to hypertension.

OBJECTIVE

This study examined the relationship between ANP Val7Met polymorphism (Single Nucleotide Polymorphism database ID: rs5063) and baseline blood pressure (BP), plasma trough irbesartan concentrations, and the antihypertensive efficacy of irbesartan in rural Chinese patients with essential hypertension.

METHODS

Patients with essential hypertension who had taken no antihypertensive medications within 4 weeks of study initiation received oral irbesartan 150 mg/d for 4 weeks. Genotyping was performed for all patients. BP was measured before dosing on the 1st and 28th days of treatment. Plasma irbesartan concentrations were measured using high-performance liquid chromatography with fluorescent detection. Antihypertensive efficacy was defined as attainment of a diastolic BP (DBP) <90 mm Hg (DBP analysis), a systolic BP (SBP) <140 mm Hg (SBP analysis), and a DBP <90 mm Hg and SBP <140 mm Hg (DBP and SBP analysis).

RESULTS

The study included 756 patients, 621 with the Val/Val genotype and 135 with the Val/Met+Met/Met genotypes. There were no significant differences in age, body mass index, sex, education level, occupation, alcohol consumption, or smoking status between the 2 groups. Patients with the Val/Met+Met/Met genotypes had a significantly lower mean baseline DBP compared with those with the Val/Val genotype (adjusted regression coefficient [SE]: -2.5 [1.0] mm Hg; P = 0.012) and significantly lower mean steady-state plasma trough irbesartan concentrations (adjusted regression coefficient: -12.6 [4.1]; P = 0.002). No significant association was found between antihypertensive efficacy and Val7Met polymorphism in the overall population, but in an analysis by baseline DBP status, patients with the Val/Met+Met/Met genotype a baseline DBP > or =100 mm Hg had significantly smaller reductions in DBP (adjusted regression coefficient: -5.7 [1.4] mm Hg; P < 0.001) and SBP compared with those with the Val/Val genotype and a baseline DBP > or =100 mm Hg (adjusted regression coefficient: -9.8 [2.9] mm Hg; P < 0.001).

CONCLUSION

The findings of this study suggest that in these rural Chinese patients with essential hypertension, ANP Val7Met polymorphism may be a genetic marker for baseline DBP, plasma irbesartan concentrations, and the antihypertensive efficacy of short-term irbesartan therapy.

B-type natriuretic peptide measurement in heart failure

Serum testing for the hormone B-type natriuretic peptide (BNP) may have clinical utility in congestive heart failure (CHF). This hormone is secreted predominantly by the left ventricular myocardium in patients with CHF. Measurement of serum BNP may improve diagnosis of CHF and may also help guide therapy in patients with CHF. The literature regarding the clinical utility of BNP measurement in CHF is reviewed.

Exercise release of cardiac natriuretic peptides is markedly enhanced when patients with coronary artery disease are treated medically by beta-blockers

OBJECTIVES

This study sought to identify determinants of the exercise rise in plasma levels of cardiac natriuretic peptides (NPs) in patients with coronary artery disease (CAD).

BACKGROUND

During stress, there is a variable rise in the plasma level of NPs, but this rise frequently reaches levels that are known to lower the cardiac load and that thus might be beneficial to CAD patients.

METHODS

Plasma venous concentrations of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) were determined at rest and peak exercise in 104 patients with chronic CAD who were referred to exercise thallium-201 ((201)Tl) single-photon emission computed tomography (SPECT) and radionuclide angiography.

RESULTS

The extent of scarred myocardium by (201)Tl-SPECT and patient age were the best independent predictors of NP concentrations at rest, but also of increases in NP concentration during exercise (all p < 0.001). Moreover, beta-blocking treatment was an additional and strong independent predictor of the increase in NP concentrations at exercise (p < 0.001 for ANP; p = 0.001 for BNP). On average, exercise increases in NP concentrations were more than twice as high in patients with (n = 55) than in those without (n = 49) beta-blocker treatment (ANP: +49 +/- 63 vs. +22 +/- 25 ng/l, p = 0.01; BNP: +24 +/- 5 vs. +11 +/- 15 ng/l, p = 0.04), whereas NP concentrations at rest were equivalent in the two groups (ANP: 34 +/- 34 vs. 30 +/- 33 ng/l, p = NS; BNP: 85 +/- 152 vs. 57 +/- 101 ng/l, p = NS).

CONCLUSIONS

Patients with chronic CAD exhibit much higher exercise releases of ANP and BNP when they are treated with beta-blockers. This enhanced secretion of potent vasodilating and natriuretic agents constitutes an original therapeutic mechanism for further protecting diseased hearts against stress.

Management of Acute Decompensated Heart Failure in the Emergency Department

Heart failure, a disease of epidemic proportions, has a tremendous clinical and financial impact on the US health care system. With more than 5 million Americans diagnosed with heart failure and 5-year mortality approaching 50%, it is the most common cause of hospitalization in patients older than 65 years and is the single most expensive diagnosis in the US health care system. Because the average US hospital loses more than 1000 dollars per heart failure admission, effective therapies that decrease length of stay, reduce hospital costs, and prevent 30-day readmissions are needed. This article reviews the relevant pathophysiology of heart failure, discusses the newest diagnostic strategies for emergency department diagnoses, evaluates recent advances and effects of early aggressive therapies, and presents a suggested algorithm for the treatment of acutely decompensated heart failure in emergency departments.

Natriuretic peptides in the diagnosis of heart disease--first amongst equals?

The natriuretic peptides and their role in neurohumoral regulation of the cardiovascular system have become the focus of considerable interest from the scientific and clinical community in recent years. BNP in particular has been shown to be an important diagnostic and prognostic marker of use in a wide range of applications. As measurement techniques develop and are refined, routine evaluation of serum levels of these markers is expected to become more widespread. We have reviewed the biochemistry of the natriuretic peptide family, their role in cardiovascular pathophysiology and the evidence supporting their use in the clinical setting.

Usefulness of carperitide for the treatment of refractory heart failure due to severe acute myocardial infarction

Carperitide (synthetic atrial natriuretic peptide) is a newly developed drug for the treatment of heart failure. Although this drug has been used for various types of heart failure, it remains unknown whether it has additive effects on hemodynamic parameters or renal excretory function during intensive treatment for acute refractory heart failure. We have examined the cardiorenal and hormonal effects of carperitide (0.05-0.10 microg / min / kg) in 9 patients (mean age: 67+/-8 years) with severe heart failure complicated with acute myocardial infarction, in which a range of intensive treatments have already been started. Hemodynamic parameters were determined before and 4, 24 and 48 hours after initiation of carperitide. Pulmonary capillary wedge pressure (mean+/-SD) had decreased dramatically from 21+/-6 to 11+/-5 mmHg (p<0.01) 4 hours after the treatment without significant renal effects. Heart rate and systemic blood pressure were not significantly changed. These beneficial effects were maintained for at least 24 hours. Plasma aldosterone levels fell significantly in response to the drug (from 148+/-68 to 56+/-29 pg / ml; p<0.05). However, mean hourly urine output remained unchanged after carperitide. In conclusion, intravenous infusion of carperitide promptly and persistently reduces left ventricular filling pressure without diuresis, hypotension, reflex tachycardia, or neurohormonal activation in patients with refractory heart failure due to severe acute myocardial infarction.

Marked and prompt hemodynamic improvement by carperitide in refractory congestive heart failure due to dilated cardiomyopathy

A 16-year-old Japanese male diagnosed with congestive heart failure (CHF) due to dilated cardiomyopathy was treated by conventional intensive treatment such as intravenous infusion of diuretics, catecholamines, and phosphodiesterase inhibitors with vasodilators. However, he developed a low output syndrome with appearances of hyponatremia and hypochloremia. As a consequence, intravenous infusion of carperitide (synthetic atrial natriuretic peptide) was added to the therapy. Thereafter his symptoms and hemodynamic parameters promptly and dramatically improved without significant diuresis, and this amelioration persisted for more than 20 days without drug intolerance. This outcome suggests that use of carperitide may be a safe and efficacious means to reduce cardiac preload without hypotension and tachycardia in patients with refractory CHF in whom intensive treatment has already been performed.

Effect of an oral contraceptive containing drospirenone on the renin-angiotensin-aldosterone system in healthy female volunteers

Drospirenone is a new synthetic progestogen with both progestational, antimineralocorticoid and antiandrogenic properties. In combination with ethinylestradiol, it is being developed as an oral contraceptive which will contain 30 micrograms ethinylestradiol and 3 mg drospirenone (Yasmin, Schering AG, Germany). The effects of drospirenone alone, and in combination with ethinylestradiol, upon the renin-angiotensin-aldosterone system (RAAS) have been evaluated in healthy female volunteers. RAAS activity was assessed by measurement of plasma renin substrate (PRS) concentration (otherwise known as angiotensinogen), plasma renin activity (PRA), and plasma aldosterone (P-Aldo) concentration. An antimineralocorticoid effect was observed when volunteers received drospirenone alone at doses in the range 0.5-3.0 mg/day for one cycle. The effect was dose-dependent for P-Aldo but was not dose-dependent for PRA. When ethinylestradiol (30 micrograms) was combined with either 2 mg or 3 mg drospirenone and given to volunteers for three cycles, an increase in PRS was observed with both preparations, which was indicative of estrogenic stimulation, and increases in PRA and P-Aldo were shown which were indicative of an antimineralocorticoid effect of drospirenone. Increases in PRA and P-Aldo were significantly higher with the preparation containing 3 mg drospirenone in cycle 1 but not in cycle 3. The effect of the preparation containing 30 micrograms ethinylestradiol/3 mg drospirenone upon RAS activity was also compared with that of a commercially available preparation also containing 30 micrograms ethinylestradiol but combined with 150 micrograms desogestrel (Marvelon). Over a period of 13 cycles, increases in PRS were seen with both treatments, the effect being slightly more pronounced with 30 micrograms ethinylestradiol/150 micrograms desogestrel. A markedly greater increase in PRA was seen following treatment with 30 micrograms ethinylestradiol/3 mg drospirenone, and, in cycle 3, this difference was statistically significant. In contrast, P-Aldo was increased markedly with 30 micrograms ethinylestradiol/3 mg drospirenone in all measured cycles, whereas, in the 30 micrograms ethinylestradiol/150 micrograms desogestrel group, changes were minimal. The increases in PRA and P-Aldo are interpreted as endogenous counter-regulation against the antimineralocorticoid activity of drospirenone. PRS increases under all combinations are an expression of estrogenic stimulation. Measurement of body weight and blood pressure in the studies with combined ethinylestradiol and drospirenone revealed that drospirenone was associated with either stable body weight or with a slight loss in body weight, while blood pressure remained largely unchanged. Overall, the results indicate that 30 micrograms ethinylestradiol/3 mg drospirenone has a distinct antimineralocorticoid effect.

Systemic hemodynamic, neurohormonal, and renal effects of a steady-state infusion of human brain natriuretic peptide in patients with hemodynamically decompensated heart failure

BACKGROUND

Human brain natriuretic peptide (hBNP) is a promising agent for the treatment of decompensated cardiac failure. However, the systemic hemodynamic, neurohormonal, and renal effects of hBNP have been incompletely studied in human heart failure.

METHODS AND RESULTS

The effects of a continuous 4-hour infusion of hBNP were determined in 16 decompensated heart failure patients in an invasive, randomized, double-blind, placebo-controlled study. Patients were evaluated during three 4-hour study periods: baseline, treatment (placebo [n = 4] versus hBNP 0.025 or 0.05 microgram/kg/min [n = 12]), and post-treatment. Urinary volume losses were replaced hourly to separate the vasodilatory and diuretic effects of hBNP. Two patients in the hBNP group were excluded from the analysis because of adverse events. hBNP significantly (P < .001) reduced right atrial pressure and pulmonary capillary wedge pressure by approximately 30% and 40%, respectively. hBNP also significantly lowered systemic vascular resistance from 1722 +/- 139 to 1101 +/- 83 dynes.s.cm-5 (P < .05). These unloading effects of hBNP produced a 28% increase in cardiac index (P < .05) with no change in heart rate. Compared to placebo, hBNP decreased plasma norepinephrine and aldosterone. Renal hemodynamics were unaffected by hBNP; however, most patients were resistant to its natriuretic effect.

CONCLUSIONS

1) The predominant hemodynamic effects of hBNP were a decrease in cardiac preload and systemic vascular resistance. 2) hBNP also improved cardiac output without increasing heart rate. 3) Plasma norepinephrine and aldosterone levels decreased during hBNP infusion. 4) hBNP is pharmacologically active and has potential in the therapy for decompensated heart failure.

C-type natriuretic peptide. An endogenous inhibitor of vascular angiotensin-converting enzyme activity

BACKGROUND

Atrial and B-type natriuretic peptide are both known to be antagonists of the renin-angiotensin system. C-type natriuretic peptide (CNP) is a new member of this family except that its principal source is the vascular endothelium. This study tested the hypothesis that CNP is a local inhibitor of vascular angiotensin-converting enzyme (ACE) activity.

METHODS AND RESULTS

Vascular ACE activity was assessed by the differential vascular response to angiotensin I and angiotensin II. Healthy male volunteers were studied with the use of brachial artery infusions of angiotensin I and angiotensin II at two doses, with and without coinfusion of CNP at 500 pmol/min (n=8) and hydralazine at 10 microgram/min (n=8) (as a nonspecific vasodilator control). CNP alone and hydralazine alone caused similar increases in forearm blood flow (CNP+, 93.0+/-14.8%; hydralazine+, 84.2+/-22.6%). CNP inhibited the vasoconstrictive effect of angiotensin I (reduction in overall effect with CNP, 56.8+/-12.9%, P<.001) but not that of angiotensin II. Hydralazine did not significantly inhibit the effect of either angiotensin I or angiotensin II.

CONCLUSIONS

This evidence of a differential effect of CNP on the vascular response to angiotensin I but not to angiotensin II suggest that CNP acts as a local endogenous regulator of vascular ACE activity in the human forearm resistance vessels.

Possible mechanisms involved in the natriuretic response to atrial natriuretic factor (ANF) and proANF 31-67 in the rat

1. The present study was conducted to compare the mechanisms involved in the natriuretic response to atrial natriuretic factor (ANF) and proANF 31-67. The peptides were infused intravenously into anaesthetized rats at 10 pmol/min for 40 min. 2. Only ANF produced a significant decrease in arterial pressure; the maximum decrease was 11 mmHg (P < 0.05). 3. Both peptides produced significant increases in sodium excretion (P < 0.05) but only ANF increased the cyclic GMP (cGMP) excretion rate (P < 0.01) and neither peptide had a significant effect on plasma renin activity or glomerular filtration rate (GFR). ProANF 31-67 did not increase the plasma levels of ANF. 4. These results demonstrate that both ANF and proANF 31-67 have natriuretic effects via a tubular mechanism and suggest that the natriuretic effects of ANF are mediated by cGMP while the excretion, changes in GFR or a reduction in renin secretion.

Rapid modulation of renal and adrenal responsiveness to angiotensin II

Reciprocal changes in adrenal and vascular responsiveness to angiotensin II (Ang II) are part of the normal adaptation to shifts in salt intake. When dietary salt intake is abruptly reduced from high to low, enhancement in aldosterone secretion requires several days to develop. Once established it is not known how quickly the enhancement is reversed with salt repletion. We investigated the time course and relative contributions of salt, volume expansion, or both to this process by studying 15 normotensive subjects; 5 were studied during both high-salt and low-salt balance, and 10 were studied only in low-salt balance. For rapid volume expansion to reverse low-salt balance, 5 subjects received in random order an infusion of normal saline or dextran. The adrenal glomerulosa and renal vascular responses to Ang II were assessed after each volume expansion maneuver. Saline and dextran infusions suppressed plasma renin activity and aldosterone equally, although dextran acted more slowly. Both also increased renal perfusion and renal vascular and pressor responses to Ang II, which in 3 to 7 hours became identical to responses seen during high-salt intake ("modulation"). Saline infusion also blunted adrenal responsiveness to Ang II during that same interval. Despite suppression of the renin-angiotensin system by dextran infusion, aldosterone responsiveness to Ang II remained enhanced. These observations suggest that the renal and vascular responses to Ang II are modulated rapidly by the effects of volume expansion per se.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of cyclic guanosine monophosphate response to infusion of atrial natriuretic peptide in young and elderly subjects

OBJECTIVE

To compare the sensitivity to atrial natriuretic peptide (ANP) in young and elderly subjects.

DESIGN

Double-blind, random-order, placebo-controlled study using two different rates of ANP infusion.

SUBJECTS

Eight healthy young (23 +/- 3 years, mean +/- SD) and eight healthy elderly (76 +/- 4 years) subjects recruited from the general population.

MEASUREMENT

Plasma cyclic guanosine monophosphate (cGMP, the second messenger of ANP) levels reflecting the sensitivity of biologically active ANP receptors.

RESULTS

Baseline ANP levels were higher and rose to a greater extent in the elderly both during low- (0.25 microgram/min) and high-dose (2.0 micrograms/min) infusion of ANP. Plasma levels of cGMP rose in proportion to the increase in ANP. When the rise in cGMP levels was related to the increase in ANP levels (expressed as nmol/L per 100 pg/mL ANP increase), no difference was found between young and elderly subjects.

CONCLUSION

The ability of elderly subjects to increase cGMP in response to exogenous ANP is similar to that of young subjects. This may reflect a similar sensitivity of the target organs towards ANP. However, because of lower clearance in the elderly, a similar dose of ANP results in a greater elevation of ANP and cGMP levels and hence induces a greater effect.

Effects of atrial natriuretic factor on the renin-aldosterone system: in vivo and in vitro studies

We investigated the effect of high physiological plasma levels of human varies; is directly proportional to atrial natriuretic factor (ANF) on renin and aldosterone secretion in normal sodium deplete men. In short term infusion studies (2 or 8 h duration), ANF plasma levels as observed after sodium loading (50-70 pg/ml) lowered basal renin (PRA) and aldosterone, but had only a marginal effect on angiotensin II-stimulated aldosterone secretion. Preliminary results of a study with long term infusion (6 days) of ANF during a period of dietary sodium depletion argue against a significant tonic inhibitory effect of ANF on the renin-aldosterone system in the preceding period of sodium repletion: the plasma aldosterone response to sodium depletion was similar with and without ANF infusion. The second messenger of ANF for the direct inhibition of aldosterone secretion from zona glomerulosa cells is still unknown. To test the hypothesis, that cGMP is the second messenger of ANF, we produced a rise in intracellular cGMP in rat and rabbit zona glomerulosa cells using the unspecific phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) and the more cGMP specific phosphodiesterase specific inhibitor M + B2948 (Zaprinast). Both inhibitors simulated the action of ANF in suppressing steroid secretion and elevating cGMP levels. The results are compatible with the view that cGMP is of importance as a second messenger for ANF in adrenal zona glomerulosa cells. Selective inhibition of phosphodiesterases in combination with endopeptidase inhibition may be an interesting principle to enhance the action of endogenous and exogenous ANF.

Beneficial effects of atrial natriuretic peptide on exercise-induced myocardial ischemia in patients with stable effort angina pectoris

BACKGROUND

It has been shown that atrial natriuretic peptide (ANP), an endogenous vasodilator, dilates coronary arteries and decreases coronary vascular resistance. The purpose of this study was to determine whether an intravenous administration of ANP attenuated exercise-induced myocardial ischemia in 14 patients with stable effort angina pectoris.

METHODS AND RESULTS

The first 12 patients (patients 1-12) who had exercise-induced ST segment depression underwent treadmill exercise testing and the last seven patients (patients 8-14) underwent the exercise 201Tl-single-photon emission computed tomography (SPECT) study while synthetic 28-amino acid alpha-human ANP (0.1 micrograms/kg per minute) or saline was intravenously infused in a double-blind, cross-over manner. The duration of exercise testing was the same during ANP and saline infusion, which was determined in preliminary exercise testings in each patient to cause a transient perfusion defect and/or ischemic ST segment depression. During saline infusion, all 12 patients developed exercise-induced ischemic ST segment depression, whereas no significant ST segment depression appeared during ANP infusion. Average ST segment depression during ANP infusion was significantly less (p < 0.01) than that during saline infusion (0.0 +/- 0.0 versus 0.2 +/- 0.1 mV, mean +/- SD). The averaged extent and severity scores assessed by 201Tl-SPECT were smaller (p < 0.05) during ANP infusion than during saline infusion (extent score: 0.22 +/- 0.20 versus 0.42 +/- 0.20; severity score: 18.77 +/- 23.45 versus 38.24 +/- 24.04, respectively). ANP decreased resting systolic blood pressure from 125 +/- 15 to 110 +/- 15 mm Hg (p < 0.01) but did not alter resting heart rate. At peak exercise, systolic blood pressure, heart rate, and the rate-pressure products did not differ during ANP and saline infusion. At peak exercise, plasma ANP increased from 98 +/- 45 to 4,383 +/- 2,782 pg/ml and cGMP increased from 3.6 +/- 1.7 to 34.5 +/- 16.1 pmol/ml during ANP infusion; values were significantly higher than those during saline infusion (from 96 +/- 42 to 133 +/- 66 pg/ml and from 3.4 +/- 1.8 to 4.6 +/- 1.8 pmol/ml, respectively).

CONCLUSIONS

An intravenous administration of ANP attenuated exercise-induced myocardial ischemia in patients with stable effort angina pectoris. Although the mechanism by which ANP attenuated myocardial ischemia was not defined, increased myocardial perfusion to the ischemic region might be an important factor.

Atrial natriuretic peptide kinetic studies in patients with cardiac dysfunction

Three studies were performed: (1) a controlled investigation of alpha-human atrial natriuretic peptide (alpha-hANP) total body production and metabolic clearance rates using a bolus infusion technique (controls, patients 1 to 6); (2) a study of alpha-hANP kinetics in cardiac dysfunction patients using a constant infusion method (patients 7 to 14); and (3) a right heart catheterization study to determine the amount of alpha-hANP released into the circulation at the level of the right heart, estimated by the step-up in alpha-hANP concentration between the superior and inferior vena cava and the pulmonary artery, in the patients with left ventricular dysfunction. Baseline venous plasma alpha-hANP was 27.3 +/- 16.5 pg/ml in the controls (mean +/- SD; N = 6), 141.6 +/- 138.0 pg/ml in patients 1 to 6 (P less than 0.05 compared to controls), and 167.5 +/- 145.7 pg/ml in patients 7 to 14. Total body alpha-hANP production rate was markedly elevated in patients 1 to 6 compared to controls (0.45 +/- 0.36 vs. 0.11 +/- 0.06 micrograms/min, P less than 0.05) and was similar to that determined by the continuous infusion technique in patients 7 to 14 (0.62 +/- 0.44 micrograms/min, P = 0.49 compared to patients 1 to 6). alpha-hANP release into the right heart (0.17 +/- 0.11 micrograms/min), however, was significantly lower than total body production rate in the cardiac dysfunction patients, indicating that total body alpha-hANP secretion occurs from sites in addition to drainage into the right heart via the coronary sinus and anterior cardiac veins. Right atrial pressure correlated with the alpha-hANP released into the right heart.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in atrial natriuretic factor and plasma renin activity in dogs infected with Trypanosoma brucei

When beagle dogs were infected with Trypanosoma brucei, a marked reduction in the plasma concentration of atrial natriuretic factor (ANF) occurred in the terminal stage of the disease during weeks 3 and 4. At the same time there was an increase in plasma renin activity (PRA) after infection. Ultrastructural studies of the atria of these dogs demonstrated a reduction in ANF granules. The changes in ANF and PRA occurred in association with severe pancarditis and the development of heart failure. By impairing the ability of the heart and kidneys to regulate blood volume, the alterations in ANF and PRA could be involved in the pathogenesis of heart failure in T. brucei-infected dogs.

[Atrial natriuretic factor in men]

The atrial natriuretic peptide (ANP) is rapidly secreted in case of acute changes in atrial volume and heart rate. Its effects are mainly natriuretic and vasodilator. This hormone is of interest to the anaesthetist because induction of anaesthesia, epidural anaesthesia and administration of morphine all result in changes in ANP plasma concentration.

Consistent changes in the circadian rhythms of blood pressure and atrial natriuretic peptide in congestive heart failure

We demonstrated in previous works that the circadian rhythms of blood pressure (BP) and atrial natriuretic peptide (ANP) are antiphasic in normal subjects and in essential hypertension. The aim of the present study was to assess the circadian rhythms of BP and ANP in 20 patients with stable congestive heart failure (CHF), divided into two groups of 10 according to their New York Heart Association functional class. A matched control group of 10 normal volunteers was also studied. Noninvasive BP monitoring at 15-min intervals was performed for 24 h. Peripheral blood samples were also obtained at 4-h intervals starting from 08:00 h. The mean (+/- SEM) circadian mesors of ANP plasma levels were 13.4 +/- 1.7 pmol/L in the control group, 28.6 +/- 2.4 pmol/L in the group of 10 patients in class II, and 81.5 +/- 12 pmol/L in the group of 10 patients in class III-IV. In normal subjects, plasma ANP concentration was highest at 04:00 h (21.5 +/- 2.7 pmol/L) and lowest at 16:00 h (8.8 +/- 2.4 pmol/L; p less than 0.01). Both groups of patients with CHF showed no significant circadian change in the plasma levels of ANP and also a significantly blunted circadian rhythm of BP. Cosinor analysis confirmed the loss of the circadian rhythms of ANP and BP in CHF patients. Our findings support the existence of a causal relationship between the circadian rhythms of ANP and BP.

Atrial strain is the main determinant of release of atrial natriuretic peptide

We studied the response of atrial natriuretic peptide to the hemodynamic and renin-aldosterone variations occurring in four patients who developed cardiac tamponade, either occurring in idiopathic fashion in one or secondary to metastatic involvement of the pericardium in three. Right atrial pressure, heart rate and arterial blood pressure were monitored and serial blood samples were taken before and over three hours after pericardiocentesis. During cardiac tamponade, normal levels of atrial natriuretic peptide (mean +/- SEM: 54 +/- 7.4 pg/ml) were observed in the plasma despite increased right atrial pressure (23 +/- 3.8 cm H2O) and heart rates (98 +/- 4.4). Removal of pericardial fluid (540 to 1160 ml) was associated at first with a 200% increase in plasma concentrations of atrial natriuretic peptide (108 +/- 8.8 pg/ml; P less than 0.001), then with a gradual decline toward normal levels, simultaneous with the normalization of right atrial pressure and heart rate. Activity of renin and concentrations of aldosterone in the plasma were increased during tamponade and returned gradually to normal after pericardiocentesis (3.8 +/- 0.9 to 1.2 +/- 0.3 ng/ml/h and 20 +/- 4.2 to 9 +/- 3.2 ng/dl, respectively; P less than 0.01). These data confirm that atrial strain, not intracavitary pressure in itself nor heart rate, is the main determinant of the acute release of atrial natriuretic peptide, which is associated with a suppressing effect on the renin-aldosterone system. In addition, our data indicate that secretion of atrial natriuretic peptide during cardiac tamponade is not stimulated by secondary hyperaldosteronism.

Endocrine activity of the "silent" adrenocortical adenoma is uncovered by response to corticotropin-releasing hormone

The purpose of this study was to ascertain whether the pituitary-adrenal responses to human corticotropin-releasing hormone (hCRH) in "non-functioning" adrenocortical adenoma would uncover a functional activity in these adrenal nodules. Eleven patients with incidentally discovered "silent" adrenocortical adenoma and eleven controls were studied. The initial clinical and laboratory examination, including an overnight 1 mg dexamethasone suppression test, revealed no abnormalities in any of the subjects. IR-ACTH and serum steroids (F, S, P, 17OHP, 18OHB, and aldosterone) were normal in both controls and patients. After pulse IV injection of 100 micrograms hCRH, the cortisol response was significantly exaggerated (P = 0.01). Stimulated plasma ACTH levels were, however, significantly lower in patients than in controls (P = 0.01), indicating counter-feedback regulation of cortisol. The peak cortisol/peak ACTH ratio (Fmax/ACTHmax) in the patients was significantly elevated (26.8 +/- 4.37 nmol/ng vs. 14.6 +/- 2.16 nmol/ng, P = 0.02). Two further patients with incidentally discovered "pre-Cushing's" adrenocortical adenoma displayed an even higher ratio (43.5 and 45.5 nmol/ng). In established Cushing's syndrome due to an autonomous adrenocortical adenoma, suppression of ACTH and of the ACTH response to hCRH occurs with a very high basal cortisol/basal ACTH ratio. Our findings suggest some functional activity even in clinically "silent" adrenocortical adenoma. Response to hCRH uncovers a continuous spectrum between adrenocortical adenoma, "pre-Cushing's", and Cushing's syndrome.

[Atrial natriuretic factor]

Although ANF research started 30 years ago, the atrial natriuretic factor (ANF) was only discovered recently (1981). The presence of such a factor has been suspected for many years because of histological and physiological arguments. In 1956, Kish found "dense granules" in the atrial walls of guinea pigs. Gauer and Henry could explain some of their experimental results on diuresis and natriuresis only by suggesting the presence of a third hormonal factor, but neither by the renin-angiotensin system, nor the anti-diuretic hormone. Hall et al. were the first to recognize a link between the granules and water and sodium metabolism. But it was De Bold who published the crucial experiment in 1981: injecting right atrial extracts to anaesthetized rats rapidly induced intense and transitory diuresis and natriuresis. ANF was born, and, at the same time, the concept of the heart as an endocrine gland. Indeed, ANF corresponds to the strict definition of a hormone. It has the following properties: natriuresis and diuresis via an increase in glomerular filtration fraction without any major changes in renal plasma flow; direct vasodilation of the large arteries with only few effects on small arterioles and veins. The stimuli for ANF secretion are mechanical and pharmacological, especially drugs currently used by anaesthetists. Atrial distension is the main mechanical stimulus. An increase in atrial transmural pressure is always followed by a release in ANF, but this effect is not constant for increases in intra-luminal pressure. It is the former pressure gradient alone that reflects the volume of the right atrium, the mechanical stimulus for ANF secretion. Tachycardia, or, more precisely, an increase in the atrial contraction rate, also leads to an important release of ANF. Cardiac nerves are not necessary for this, as demonstrated by studies in heart transplant patients. Only few pharmacological agents have been shown to really stimulate ANF secretion. In rats, morphine has a direct secretory effect, whereas ketamine hydrochloride, diethylether and chloral hydrate do so by increasing the release of catecholamines. The effects of alpha, beta adrenergic agonists and calcium agonists remain controversial. ANF, which has diuretic and vasodilator effects, plays a part, together with the renin-angiotensin system and the anti-diuretic hormone, in blood volume control in mammals. However, it has a special role to play, because it is a rapid release hormone: rapid vascular filling leads to an increase in ANF in less than 1 minute, with a parallel increase in diuresis.

Atrial natriuretic hormone and aldosterone regulation in salt-depleted state

To evaluate the effect of very low-dose infusion of atrial natriuretic hormone (ANH) on aldosterone regulation, seven normal young men were infused for 2.5 h with 0.47 pmol.kg-1.min-1 of human [Ser-Tyr28]ANH or placebo. During the last 0.5 h 4 pmol.kg-1.min-1 of angiotensin II were also infused. ANH plasma levels increased from 3.46 +/- 0.25 to a maximum of 6.80 +/- 0.88 pmol/l, which is well within normal limits. Plasma aldosterone decreased almost 40%, from 40.7 +/- 5.7 to 25.9 +/- 4.9 ng/dl after 2 h. ANH infusion caused a slight decrease in blood pressure and slight increase in renal excretion of sodium and potassium. These results suggest that even small changes in ANH levels, within the normal range, have physiological significance, particularly in aldosterone regulation.