Plasma atrial natriuretic peptide and renin-aldosterone in patients with cirrhosis and ascites: basal levels, changes during daily activity and nocturnal diuresis

Overexpression of kidney neutral endopeptidase (EC 3.4.24.11) and renal function in experimental cirrhosis

Neutral endopeptidase degrades atrial natriuretic peptide (ANP) and bradykinin and may generate endothelin-1 from big-endothelin. In advanced cirrhosis, sodium retention is accompanied by elevated plasma ANP levels, and infusion of ANP causes hypotension, but in normal humans increasing the concentration of ANP through the inhibition of neutral endopeptidase, localized in renal proximal tubule cells, causes natriuresis without any arterial pressure drop. The purpose of this study was the assessment of kidney neutral endopeptidase expression and responses to candoxatrilat (a specific inhibitor of this enzyme) in rats with CCl4-induced cirrhosis. Two groups of control rats ( n = 5) were injected with vehicle or 3 mg/kg candoxatrilat. Three groups of cirrhotic rats with ascites ( n = 10) received vehicle alone or 3 or 10 mg/kg candoxatrilat. In cirrhotic rats, Western blot analysis revealed a 170% increase in renal neutral endopeptidase protein content ( P < 0.03), mainly in the proximal nephron and macula densa, and both candoxatrilat dosages increased plasma ANP levels, urinary volume, and urinary excretion of sodium, ANP, and cGMP compared with vehicle alone (all P < 0.03). Candoxatrilat (10 mg/kg) also reduced tubular solute-free water reabsorption ( P < 0.03) in cirrhotic rats, but renal blood flow, arterial pressure, and plasma renin activity were unaffected. Neutral endopeptidase inhibition has natriuretic and aquaretic actions in cirrhosis without any effect on blood pressure and kidney perfusion due to a significant overexpression of this enzyme in renal cortex.

Increased arterial compliance in cirrhosis is related to decreased arterial C-type natriuretic peptide, but not to atrial natriuretic peptide

BACKGROUND

Increased arterial compliance (COMPart) has recently been described in patients with cirrhosis, particularly in advanced disease. The aim of the present study was to relate COMPart with arterial levels of the circulating natriuretic peptides: atrial natriuretic peptide (ANP) and C-type natriuretic peptide (CNP), both of which are vasodilators.

METHODS

Thirty-one patients with cirrhosis, 14 non-cirrhotic patients with circulatory disturbances of the ischaemic and hypertensive type, and 10 healthy controls were investigated during a haemodynamic examination.

RESULTS

The patients with cirrhosis showed the well-known hyperdynamic circulation with elevated cardiac output, low arterial blood pressure, and reduced systemic vascular resistance. COMPart in the patients with cirrhosis (1.30 mL/mmHg) was significantly (P < 0.01) increased compared to that of non-cirrhotic patients (0.99 mL/mmHg) and controls (1.01 mL/mmHg). In the patients with cirrhosis, a significant inverse correlation was found between CNP and COMPart (r = -0.42, P < 0.01), but not between CNP and systemic vascular resistance (r = 0.31, P = 0.08). In the non-cirrhotic patients, CNP had a significant inverse correlation to COMPart (r = -0.68, P < 0.01) and a direct correlation to systemic vascular resistance (r = 0.62, P < 0.02). ANP was not significantly related to COMPart nor to systemic vascular resistance in any of the groups.

CONCLUSION

The finding of an inverse relation between CNP and COMPart may suggest that a compensatory down-regulation of CNP occurs in patients with cirrhosis and other types of circulatory disorders when vasodilation persists. Regulation of large and small arteries by CNP may be different in cirrhosis. Arterial ANP is not related to properties of the large or small arteries.

Effect of upright posture and physical exercise on endogenous neurohormonal systems in cirrhotic patients with sodium retention and normal supine plasma renin, aldosterone, and norepinephrine levels

It is well known that sodium retention occurs in a significant proportion of patients with cirrhosis despite normal supine plasma levels of renin, aldosterone (ALDO), and norepinephrine (NE). The current study was performed to assess whether this subset of patients also present normal activity of the renin-aldosterone and sympathetic nervous systems during upright posture in sitting position and moderate physical exercise. Nine healthy controls, 14 patients with compensated cirrhosis and 10 patients with cirrhosis, ascites, sodium retention, and normal supine plasma renin activity (PRA) and ALDO and NE concentration were sequentially studied after 60 minutes in supine rest, 30 minutes in sitting position, and 30 minutes of cycloergometric exercise (3-METs). Sitting position and exercise were associated with similar stimulation of the renin-aldosterone and sympathetic nervous systems in the three groups of subjects. Consequently, cirrhotic patients with ascites showed values of PRA and plasma concentration of ALDO and NE similar to healthy subjects and patients with compensated cirrhosis during supine rest (renin: 1.4 +/- 0.3, 0.8 +/- 0.2, and 0.8 +/- 0.3 ng/mL; aldosterone: 24.3 +/- 4.7, 20.2 +/- 3.9 and 21.4 +/- 3.4 ng/dL; norepinephrine: 252 +/- 23, 250 +/- 16, and 255 +/- 23 pg/mL), sitting position (renin: 2.1 +/- 0.5, 1.1 +/- 0.3, and 1.6 +/- 0.4; aldosterone: 32.2 +/- 7.3, 23.7 +/- 5.3, and 26.2 +/- 4.5; norepinephrine: 356 +/- 38, 401 +/- 63, and 420 +/- 35), and exercise (renin: 2.9 +/- 0.8, 1.6 +/- 0.4, and 2.2 +/- 0.5; aldosterone: 43 +/- 6.4, 34.9 +/- 8.5, and 38.2 +/- 5.3; norepinephrine: 481 +/- 35, 499 +/- 54, and 534 +/- 48).(ABSTRACT TRUNCATED AT 250 WORDS)

The role of atrial natriuretic peptide (ANP) in chronic liver disease

The role of atrial natriuretic peptide (ANP) and potential defects of ANP in liver disease are reviewed. Patients with cirrhosis of the liver show no decrease of ANP plasma concentrations nor changes in the pattern of ANP immunoreactivity nor changes of splanchnic ANP clearance. The renal effects of exogenously administered as well as endogenously released ANP are blunted in cirrhosis, in particular in patients with ascites. This seems due to increased activity of sodium-retaining hormonal systems and changes of the renal ANP receptor status. Pharmacological inhibition of ANP-degradation or clearance may yield therapeutic potential.