Plasma atrial natriuretic peptide in young normotensive subjects with a family history of hypertension and in young hypertensive patients

A review of vasopeptidase inhibitors: a new modality in the treatment of hypertension and chronic heart failure

Vasopeptidase inhibitors are a group of agents capable of inhibiting neutral endopeptidase and angiotensin-converting enzymes, which leads to potentiation of natriuretic peptide actions and suppression of the renin-angiotensin-aldosterone system. With this distinctively characteristic mechanism, these agents have emerged as a new drug class for management of hypertension and heart failure. Several vasopeptidase inhibitors are under clinical investigation. Omapatrilat is the most studied agent in this class. Clinical studies of omapatrilat in hypertension have consistently shown the agent's effectiveness in a variety of patient populations. In patients with heart failure, omapatrilat significantly improved neurohormonal and hemodynamic status. Long-term effects of omapatrilat in patients with heart failure recently were compared with those of conventional therapy in a large phase II trial. Results of the study appear promising. Large clinical trials are ongoing, and additional information regarding safety and efficacy from these studies may help define the place in therapy for this agent.

Relationship of diastolic blood pressure with cyclic GMP excretion among young adults (the CARDIA Study): influence of a family history of hypertension. Coronary Artery Risk Development in Young Adults

BACKGROUND

Guanosine 3':5'-cyclic monophosphate (cGMP) is the second messenger of nitric oxide and atrial natriuretic factor, and mediates local vasodilatation. These vasodilatory factors are important in blood pressure regulation and possibly in the etiology of hypertension. Urinary cGMP levels among normotensive young adults have not previously been studied.

SUBJECTS

A subset of normotensive participants from the CARDIA study (n = 563), aged 23-35 years, was studied. The sample was approximately balanced for sex and race (black/white).

METHODS

Twenty-four-hour urinary cGMP levels were measured using an enzyme immunoassay; levels were adjusted for creatinine excretion. The blood pressure, smoking status, and risk factors for hypertension [including a family history of hypertension (FHH), the body mass index, education, alcohol intake, and sodium excretion] were also measured.

RESULTS

Women excreted more cGMP than did men, and blacks excreted more cGMP than did whites (both P < 0.0001). Excretion of cGMP was also greater among smokers (P < 0.001) and those with an FHH (P = 0.05), and was related directly and independently to sodium excretion (P < 0.02). The diastolic blood pressure (DBP) was related inversely to the excretion of cGMP among individuals without an FHH (r = -0.36, P < 0.001), but not among individuals with an FHH. In multiple regression analysis, the excretion of cGMP remained related significantly to the DBP and accounted for more variance in DBP than did any other variable among those without an FHH (delta R2 = 0.08, P < 0.001).

CONCLUSIONS

Urinary cGMP excretion is related inversely and independently to the DBP among those without an FHH but not among those with an FHH, suggesting that cGMP-related vasodilatation is impaired in those with an FHH. Sex differences in urinary excretion of cGMP are consistent with results from studies showing that estrogen increases the endothelial production of nitric oxide.

Atrial natriuretic peptide and blood pressure in a population-based sample

OBJECTIVE

To assess the relationship of plasma atrial natriuretic peptide (ANP) levels with blood pressure levels and the occurrence of hypertension in a large population-based sample.

DESIGN

We performed a cross-sectional study of the relationship between ANP levels and blood pressure levels, diagnosis of hypertension, and family history of hypertension in Caucasians from Rochester, Minnesota.

MATERIAL AND METHODS

Plasma ANP and blood pressure levels were measured in 1,338 Caucasian subjects who were members of 301 three-generation families from the population of Rochester. Hypertension was defined as systolic blood pressure of 140 mm Hg or more or diastolic blood pressure of 90 mm Hg or more. Each subject in the parental generation was categorized as having zero, one, or two parents with hypertension. Analyses were done separately for each generation and gender stratum.

RESULTS

Within gender and generation strata, we noted no consistent pattern of positive or negative correlation of plasma ANP levels with systolic blood pressure, diastolic blood pressure, or heart rate. Within the grandparental generation, mean plasma ANP levels did not differ between those with normal blood pressure and those with hypertension. In the parental generation, mean plasma ANP levels did not differ between subjects with zero, one, or two parents with hypertension.

CONCLUSION

In Caucasians, interindividual differences in plasma ANP levels are not associated with interindividual differences in blood pressure levels, the diagnosis of hypertension, or family history of hypertension.

Atrial natriuretic peptide and its potential role in pharmacotherapy

Atrial natriuretic peptide (ANP) is a 28 amino-acid polypeptide secreted into the blood by atrial myocytes after atrial pressure and distension. Although its role in humans is not clear, it can produce a variety of physiologic effects including vasodilatation, natriuresis, and suppression of the renin-angiotensin-aldosterone axis. These actions are potentially useful in a variety of pathologic states such as hypertension and congestive heart failure, and diverse methods to augment the effects of ANP in these states have been devised. The results are exciting and, despite some problems, may lead to the pharmacologic use of enhancement of ANP actions in several clinical disorders.

Abnormal atrial natriuretic peptide and renal responses to saline infusion in nonmodulating essential hypertensive patients

BACKGROUND

Nonmodulation seems to represent an inheritable trait characterized by abnormal angiotensin-mediated control of aldosterone release and renal blood supply and salt-sensitive hypertension. Recently, we demonstrated that atrial natriuretic peptide (ANP) response to angiotensin II also is altered in nonmodulators. Moreover, an abnormal ANP response to acute volume expansion has been shown by others in hypertensive patients displaying some features of nonmodulators. These data induced us to hypothesize that nonmodulators. These data induced us to hypothesize that nonmodulation could be characterized by an abnormal ANP response to saline load.

METHODS AND RESULTS

Forty-three essential hypertensive men were subdivided into low-renin patients (n = 12), nonmodulators (n = 15), and modulators (n = 16) according to their renin profile and ability to modulate aldosterone and p-aminohippurate clearance responses to a graded angiotensin II infusion (1.0 ng.kg-1.min-1 and 3.0 ng.kg-1.min-1 for 30 minutes each) on both a low- (10 mmol Na+ per day) and a high- (210 mmol Na+ per day) Na+ intake. The intravenous saline load (0.25 mL.kg-1.min-1 for 2 hours) performed on a low-Na+ diet increased plasma ANP levels in low-renin (from 14.30 +/- 4.68 to 23.30 +/- 7.52 fmol/mL at 120 minutes, P < .05) and modulating patients (from 10.95 +/- 3.55 to 18.21 +/- 5.42 fmol/mL at 120 minutes, P < .05), whereas it did not change the hormone levels in nonmodulators (from 10.77 +/- 3.25 to 13.83 +/- 5.70 fmol/mL at 120 minutes, P = NS). When patients switched from a low- to a high-NaCl diet, plasma ANP levels increased significantly in all groups. However, when the saline load was repeated on a high-NaCl intake, ANP levels increased in both low-renin and modulating patients (P < .05), whereas it failed to increase in nonmodulators.

CONCLUSIONS

Nonmodulating hypertensive patients showed a reduced ANP response to saline infusion in the presence of a normal increase of plasma ANP with dietary NaCl load. The impaired ANP response to saline infusion could be due to a different distribution of volume load and contribute to determining the reduced ability to excrete sodium that is commonly described in nonmodulators.

The Bergen Blood Pressure Study: inappropriately low levels of circulating atrial natriuretic peptide in offspring of hypertensive families

Plasma atrial natriuretic peptide (ANP), plasma and 24-h urine catecholamines, plasma renin activity (PRA), and serum aldosterone were studied in offspring of hypertensive and normotensive families [n = 82; age 37 +/- 7 years (mean +/- SD)]. Despite higher age, higher blood pressure, and higher urine excretion of catecholamines--all of which are factors associated with increased ANP levels--the mean basal plasma ANP concentration tended to be lower in offspring of hypertensive than normotensive families. The same pattern was found in all age-tertiles, and the between-group difference was statistically significant in subjects aged 34-39 years (p < 0.01). Also, the family history of hypertension was associated with low ANP levels after covariate adjustment (p < 0.05). The 24-h urine excretion of epinephrine and norepinephrine tended to be higher in offspring of hypertensive than normotensive families while the morning venous plasma levels were similar. The ratio between venous plasma ANP and norepinephrine was lower in offspring of hypertensive than normotensive families (p < 0.05). PRA, serum aldosterone level, and 24-h urine excretion of dopamine did not differ significantly between groups. Inappropriately low basal plasma ANP concentrations and low plasma ANP/norepinephrine ratios may be related to the development of essential hypertension in offspring of hypertensive families.

Effects of atrial natriuretic factor infusion on plasma prorenin levels in hypertensive males

To evaluate the influence of atrial natriuretic factor (ANF) infusion on circulating prorenin, 20 essential hypertensive males, aged between 40 and 60 years, were studied. After 2 weeks under normal sodium intake (120 mmol NaCl per day), patients were randomly assigned to receive either ANF (0.01 fmol/Kg/min) (n.12 patients) or its vehicle (50 mL of isotonic saline) (n.8 patients) over a period of 60 minutes. Blood samples for plasma renin activity (PRA), prorenin and aldosterone (PAC) were taken at time -60, 0, 20, 40, 60, 120, 180, 240 minutes (infusion time: from 0 to 60 minutes). PRA and PAC decreased during the ANF infusion (PRA: from 0.33 +/- 0.05 ng/L/s at time 0 to 0.10 +/- 0.06 ng/L/s at 60 minutes, p < 0.0001; PAC: from 389.2 +/- 99.8 pmol/L at time 0 to 148.7 +/- 44.3 pmol/L at 60 minutes, p < 0.0001), while returned immediately to baseline levels after the infusion was stopped (PRA: 0.37 +/- 0.11 ng/L/s at 180 minutes, PAC: 251.6 +/- 72.1 pmol/L at time 180 minutes). On the contrary, plasma prorenin increased during ANF infusion (from 1.66 +/- 0.58 ng/L/s at time 0 to 2.44 +/- 0.72 ng/L/s at 60 minutes, p < 0.05), and returned to baseline levels after the end of the infusion (1.86 +/- 0.83 ng/L/s at 180 minutes). These data indicate that ANF infusion may alter only the circulating levels of active renin, without affecting plasma prorenin secretion.

Atrial natriuretic peptide in non-modulating essential hypertension

To evaluate the atrial natriuretic peptide response to angiotensin II (Ang II) infusion in non-modulating hypertension, we studied 31 men with essential hypertension. These patients were subdivided into groups of low renin patients (n = 8), non-modulators (n = 11), and modulators (n = 12) according to their renin profile and ability to modulate renin and aldosterone responses to a graded infusion of Ang II (1.0 and 3.0 ng/kg per minute) on a low Na+ intake (10 mmol Na+ per day). During basal conditions, plasma atrial natriuretic peptide was higher (p < 0.05) in low renin patients (16.34 +/- 2.67 fmol/mL) than in both modulators (10.59 +/- 4.29 fmol/mL) and non-modulators (9.85 +/- 2.64 fmol/mL). During Ang II infusion, plasma atrial natriuretic peptide significantly increased in both low renin (27.67 +/- 2.61 fmol/mL at 60 minutes, p < 0.01) and modulating (20.36 +/- 3.07 fmol/mL at 60 minutes, p < 0.05) patients, whereas it did not change in non-modulators (13.94 +/- 4.39 fmol/mL, NS). After 5 days on a high sodium intake (200 mmol Na+ per day), plasma atrial natriuretic peptide rose in modulating (20.61 +/- 2.31 fmol/mL, p < 0.01 versus low sodium intake), non-modulating (20.11 +/- 6.48 fmol/mL, p < 0.01 versus low sodium intake), and low renin (26.13 +/- 3.81 fmol/mL, p < 0.001 versus low sodium intake) hypertensive patients. When the Ang II infusion was repeated with a high sodium intake, plasma atrial natriuretic peptide increased again in low renin and modulating patients, whereas it did not change in non-modulators.(ABSTRACT TRUNCATED AT 250 WORDS)

Pathogenesis of the essential hypertensions

The pathogenesis of essential hypertension (EH) is reviewed with a special focus on the development phase or the pre-hypertensive period. Three animal models are presented: the spontaneously hypertensive rat, the Dahl's salt-sensitive rat, and the Milan hypertensive rat. Some of the findings in animal models have inspired new fields and technical approaches for studying EH in man. From the original idea of Page, a new mosaic of various etiological parameters serves as a basis for reviewing the multiple facets of EH in man. One must conclude that EH is heterogeneous disease and most likely every single hypertensive patient belongs to a subgroup of the whole population of hypertensives.