Blunted natriuretic response and low blood pressure after atrial natriuretic factor in early cirrhosis

Effects of urodilatin on natriuresis in cirrhosis patients with sodium retention

BACKGROUND

Sodium retention and ascites are serious clinical problems in cirrhosis. Urodilatin (URO) is a peptide with paracrine effects in decreasing sodium reabsorption in the distal nephron. Our aim was to investigate the renal potency of synthetic URO on urine sodium excretion in cirrhosis patients with sodium retention and ascites.

METHODS

Seven cirrhosis patients with diuretics-resistant sodium retention received a short-term (90 min) infusion of URO in a single-blind, placebo-controlled cross-over study. In the basal state after rehydration the patients had urine sodium excretion < 50 mmol/24 h.

RESULTS

URO transiently increased urine sodium excretion from 22 +/- 16 micromol/min (mean +/- SD) to 78 +/- 41 mumol/min (P < 0.05) and there was no effect of placebo (29 +/- 14 to 44 +/- 32). The increase of URO's second messenger after the receptor, cGMP, was normal. URO had no effect on urine flow or on blood pressure. Most of the patients had highly elevated plasma levels of renin, angiotensin II and aldosterone and URO did not change these.

CONCLUSION

The short-term low-dose URO infusion increased the sodium excretion of the patients. The increase was small but systematic and potentially clinically important for such patients. The small response contrasts the preserved responsiveness of the URO receptors. The markedly activated systemic pressor hormones in cirrhosis evidently antagonized the local tubular effects of URO.

Neutral endopeptidase (EC 3.4.24.11) in cirrhotic liver: a new target to treat portal hypertension?

BACKGROUND/AIMS

In liver cirrhosis atrial natriuretic peptide (ANP) decreases portal vascular resistance and tributary flow. The enzyme neutral endopeptidase (NEP) degrades ANP and bradykinin and generates endothelin-1 from big-endothelin. We determined the effects of NEP inhibition by candoxatrilat on hormonal status, liver function and arterial and portal pressures in rats with CCl4-induced cirrhosis.

METHODS

Two groups of seven control rats received 1 ml 5% glucose solution alone or containing 10 mg/kg candoxatrilat; three groups of 10 ascitic cirrhotic rats received placebo, 5 or 10 mg/kg candoxatrilat. NEP protein concentration and immunostaining were analyzed in normal and cirrhotic livers.

RESULTS

In cirrhotic rats 10 mg/kg candoxatrilat significantly increased steady-state indocyanine green clearance (a parameter reflecting liver plasma flow) (P<0.01), decreased portal pressure (P<0.01), had no effect on arterial pressure and plasma renin activity but increased ANP plasma levels (P<0.05) and urinary excretions (P<0.01) of ANP and cGMP. In the cytosol fraction of rat cirrhotic livers a 280% increase in NEP content was found (P<0.01), chiefly localized in desmin-positive myofibroblast-like cells of fibrous septa.

CONCLUSIONS

Candoxatrilat has few effects on systemic hemodynamics and hormonal status; its portal hypotensive action depends on effects exerted on intrahepatic vascular resistance.

Prevention of Renal Impairment by Continuous Infusion of Human Atrial Natriuretic Peptide after Liver Transplantation

BACKGROUND

Acute renal failure occurring immediately after liver transplantation and requiring hemodialysis is a major problem resulting in a poor prognosis. We investigated the efficacy of human atrial natriuretic peptide, which has potent natriuretic effects and unique protective effects for glomeruli in preventing acute renal failure after liver transplantation.

METHODS

Thirty-seven patients who underwent live donor liver transplantation with model for end-stage liver disease scores greater than 15 were the subjects of the study. Subjects were prospectively randomized into two groups: patients that received synthetic human atrial natriuretic peptide infusion (Group H: n=19) and those that received conventional diuretics, furosemide and potassium canrenoate (Group C: n=18). The peri- and postoperative changes in hemodynamic status and renal function were compared between the two groups.

RESULTS

There were no statistical differences in the changes in hemodynamic status between groups. Hemodialysis was required after liver transplantation in nine patients, two in Group H and seven in Group C (P=0.04). Postoperative creatinine clearance was higher in Group H (P=0.03). Aldosterone level was suppressed in group H (P=0.006).

CONCLUSIONS

Continuous infusion of synthetic human atrial natriuretic peptide might be effective for preventing acute renal failure requiring hemodialysis after liver transplantation.

Gastric functions in portal hypertension. Role of endothelin

This study investigated the effects of portal hypertension on gastric motor and secretory functions and the role of endothelin in rats. Control; sham-operated; endothelin-A receptor blocker, BQ 485 (1 microgram/kg)-treated; portal hypertensive; and portal hypertension +, endothelin-A receptor blocker-treated rats were subjected to tests of gastric secretory, motor, and mucosal function studies as well as gastric wall polymorphonuclear infiltration. Portal hypertension was induced by partial portal vein ligation. Portal hypertension suppressed gastric acid and total fluid secretion and delayed gastric emptying. An increase in mucosal permeability and no alteration in gastric wall myeloperoxidase activity were observed. The effects of portal hypertension on gastric secretory, motor, and mucosal functions were reversed by treatment with endothelin-A receptor blocker, BQ-485. It is concluded that portal hypertension suppresses the gastric motor and secretory functions and endothelin plays an important role in the pathophysiology of gastric alterations associated with portal hypertension.

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)

Effects of high dose atrial natriuretic peptide on renal haemodynamics, sodium handling and hormones in cirrhotic patients with and without ascites

To elucidate and to try to reverse the antinatriuretic mechanisms in liver cirrhosis, atrial natriuretic peptide (ANP) was given as a pharmacological bolus dose (2 micrograms per kg body weight) to 14 cirrhotic patients, and as a control to 14 healthy subjects. The nine patients with ascites had baseline values of glomerular filtration rate (GFR), effective renal plasma flow (ERPF) and blood pressure (BP) similar to controls. Their distal tubular fractional reabsorption of sodium (DFRNa), estimated by the lithium clearance technique, was higher than in controls, and so were plasma values of aldosterone (564 vs. 119 pmol l-1 medians), endothelin (1.23 vs. 0.63 pmol l-1), ANP (7.5 vs. 3.6 pmol l-1) and cyclic GMP (8.8 vs. 4.6 nmol l-1); p < 0.01 for all. The five patients without ascites had higher GFR and ERPF, and lower plasma angiotensin II than controls. After ANP injection, similar plasma levels of ANP and cyclic GMP were reached in all groups. Urinary sodium excretion rate increased in controls (0.23 to 0.52 mmol min-1, p < 0.01), while GFR increased (108 to 117 ml min-1, p < 0.05), and DFRNa decreased (93 to 89%, p < 0.01). In cirrhotics with ascites sodium excretion was unaltered (0.12 to 0.11 mmol min-1), and so was GFR (84 to 83 ml min-1). Proximal tubular fractional reabsorption of sodium increased after 90 min, whereas DFRNa decreased immediately (97 to 96%, p < 0.01) though less markedly than in controls. Sodium excretion increased in four of five patients without ascites (0.23 to 0.27 mmol min-1, medians). In patients with ascites, endothelin in plasma decreased after ANP (p < 0.05). Plasma levels of angiotensin II, aldosterone and vasopressin were unchanged in all groups. In conclusion, although hyper-reabsorption of sodium occurred in the distal rather than the proximal part of the nephron in cirrhotic patients with ascites, ANP had no natriuretic effect. This was most probably due primarily to the lack of increase of GFR and blunted inhibition of DFRNa, attributed to high aldosterone. The effect of ANP in suppressing the high endothelin did not seem to improve sodium excretion.

Blunted natriuresis and abnormal systemic hemodynamic responses to C-type and brain natriuretic peptides in rats with cirrhosis

BACKGROUND/AIMS

The effects of C-type and brain natriuretic peptides (CNP and BNP, respectively) on renal excretion of sodium and hemodynamics have not yet been studied in cirrhosis.

METHODS

This study aimed to examine the effects of saline, CNP (300 ng.kg-1.min-1 i.v. for 30 min) and BNP (600 ng.kg-1.min-1 i.v. for 30 min) on natriuresis and diuresis in normal and rats with cirrhosis. Moreover, regional and systemic hemodynamics were measured prior to and following CNP and BNP administration in normal rats and rats with cirrhosis with ascites.

RESULTS

In rats with cirrhosis, the effects of CNP or BNP or natriuresis and diuresis did not significantly differ from the effects of saline. CNP significantly decreased portal pressure and systemic vascular resistance and significantly increased the cardiac index. BNP significantly decreased portal tributary blood flow, portal pressure and cardiac index. In normal rats, natriuresis and diuresis were significantly higher with CNP and BNP than with saline. Systemic hemodynamics were not changed by CNP. A decrease in arterial pressure was the sole BNP-induced hemodynamic change.

CONCLUSIONS

In conclusion, this study shows that the natriuretic response to pharmacological doses of CNP and BNP is blunted in rats with cirrhosis. This blunting may be related to an activation of the endogenous antinatriuretic systems secondary to systemic vasodilation (by CNP) or to a decreased cardiac index (by BNP). Finally, this study shows that CNP and BNP have a portal hypotensive action.

Renal sodium retention during upright posture in preascitic cirrhosis

BACKGROUND

Renal sodium handling in preascitic cirrhosis is not clearly defined. This issue was addressed by evaluating renal sodium metabolism with different postures.

METHODS

Renal function and plasma atrial natriuretic factor (ANF), aldosterone, and norepinephrine levels were determined after 2 hours of standing and 30, 60, and 120 minutes after taking up the supine position in 10 patients and 10 healthy subjects.

RESULTS

When upright, patients' glomerular filtration rate and plasma ANF and norepinephrine levels did not differ from those of controls. Conversely, renal sodium excretion was reduced. Plasma aldosterone levels, which were slightly elevated, inversely correlated with renal sodium excretion. In the supine position, natriuresis increased by 308% +/- 99% in patients and 113% +/- 29% in controls (P = 0.016), so that it no longer differed between the two groups. Plasma norepinephrine and aldosterone levels decreased to a similar extent in controls and cirrhotics, whereas the increase in plasma ANF level was greater in patients. The changes in natriuresis correlated with those in plasma ANF levels and plasma aldosterone-ANF ratios in both controls and patients.

CONCLUSIONS

Aldosterone-dependent sodium retention develops in preascitic cirrhosis during standing. The supine position is the means whereby standing-induced sodium retention can be balanced.

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.

The hemodynamic status of preascitic cirrhosis: an evaluation under steady-state conditions and after postural change

To assess the hemodynamic status of patients with compensated cirrhosis, mean arterial pressure, cardiac index and peripheral vascular resistance and markers of central (plasma concentrations of atrial natriuretic factor) and arterial volemia (plasma norepinephrine concentration, plasma renin activity) were studied in 10 patients and 10 healthy control subjects under steady-state conditions (after 2 hr of standing) and after assumption of the supine position (30, 60, and 120 min). After standing, neither hemodynamics nor markers of effective volemia differed significantly between controls and patients. By evaluating the areas under the curve during the 2 hr of supine posture, the increase in cardiac output and plasma natriuretic factor and the decrease in peripheral vascular resistance were greater in patients (2.59 +/- 0.43 [S.E.M.] L/min/hr; 32.8 +/- 7.2 pg/ml/hr -1,103 +/- 248.4 dyn.sec/cm5/hr, respectively) than in controls (0.53 +/- 0.24 L/min/hr, p = 0.005; 17.4 +/- 4.7 pg/ml/hr, p = 0.005; -265.5 +/- 206.2 dyn.sec/cm5/hr, p = 0.02). The declines in heart rate, plasma norepinephrine concentration and plasma renin activity did not differ significantly. Mean arterial pressure did not significantly change. Our results suggest that during periods of upright posture, cirrhotic patients in the preascitic stage, who are known to have expanded blood volume, compensate for dilatation of the splanchnic vascular bed through total hypervolemia. The latter becomes excessive during recumbency, leading to supernormal increases in venous return, central volemia and cardiac index. The decline in peripheral vascular resistance appears to be a compensatory mechanism to maintain steady arterial blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal effects in cirrhotic patients with avid sodium retention of atrial natriuretic factor injection during norepinephrine infusion

The administration of atrial natriuretic factor to patients with cirrhosis, and avid sodium retention causes marked hypotension and blunted kidney responses. To evaluate whether the unresponsiveness of the kidney is caused by a fall in mean blood pressure below a critical value for the renal blood perfusion pressure (80 mm Hg), we studied nine such patients and compared the effects of synthetic atrial natriuretic factor alone (1 micrograms/kg as a bolus) with those of an atrial natriuretic factor combination with infused norepinephrine titrated to raise baseline blood pressure by 15 to 20 mm Hg (182 to 625 ng/kg/min). The administration of atrial natriuretic factor during norepinephrine infusion caused a fall in mean blood pressure to values not less than 80 mm Hg in eight of nine patients, with a slight natriuresis (greater than 5 mumol/min) in five patients but no changes in the other four. The mean urinary sodium output was markedly lower than that previously observed after atrial natriuretic factor injection into normal subjects and into cirrhotic patients without avid sodium retention. Unlike sodium excretion, urine flow rate and free water clearance (which were not affected by atrial natriuretic factor alone) were markedly improved by the coadministration of norepinephrine and atrial natriuretic factor. In four additional patients we studied the urinary electrolyte excretion during a low-dose infusion of atrial natriuretic factor (20 ng/kg/min) to which an infusion of norepinephrine titrated to maintain blood pressure over 80 mm Hg was added. In only one of these four patients urinary sodium output consistently increased during atrial natriuretic factor infusion, and the output increased even more when norepinephrine was added.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamic and sympathetic responses to human atrial natriuretic peptide infusion in patients with cirrhosis

To determine the potential usefulness of atrial natriuretic peptide (ANP) in patients with cirrhosis, we examined the effects of the infusion of a low dose of alpha-human ANP (alpha hANP, 25 ng.kg-1.min-1 for 30 min) on renal, splanchnic, systemic hemodynamics and sympathetic outflow in eight patients. Pulmonary arterial plasma ANP concentrations increased from 59 +/- 9 to 328 +/- 41 pg/ml (mean +/- S.E., p less than 0.05). Mean values of glomerular filtration rate and renal plasma flow were not significantly changed. Individual renal plasma flow responses differed from one patient to another. Renal plasma flow increased in two patients, decreased in three and did not change in the other patients. Renal plasma flow changes were correlated with basal renal plasma flow values (r = -0.938, p less than 0.05) but not with arterial pressure changes or renal vein plasma norepinephrine concentration changes. Azygos blood flow increased from 0.43 +/- 0.10 to 0.63 +/- 0.13 l/min (p less than 0.05) and the hepatic-venous pressure gradient decreased from 19.9 +/- 1.5 to 17.5 +/- 2.9 mmHg in post-infusion (p less than 0.05). Mean arterial pressure decreased significantly by 18% and cardiac output by 12%. Systemic vascular resistance and pulmonary arterial plasma norepinephrine concentrations were not significantly modified. Thus, in patients with cirrhosis, alpha hANP appears to have a direct vasodilating action on renal arterioles when basal renal vascular tone is high. In addition, although alpha hANP might exert a portal hypotensive action, alpha hANP induced arterial hypotension as a result of both low cardiac output and a lack of increased sympathetic vascular tone. The arterial hypotensive action may, thus, limit the therapeutic use of low doses of alpha hANP in cirrhotic patients.

Renal insensitivity to atrial natriuretic peptide in patients with cirrhosis and ascites. Effect of increasing systemic arterial pressure

The IV infusion of pharmacological doses (0.05 microgram.kg-1.min-1) of atrial natriuretic peptide to 16 patients with cirrhosis and ascites induced a significant increase in sodium excretion (65 +/- 23 to 517 +/- 231 mu Eq/min), urine volume (10.7 +/- 2.3 to 15.7 +/- 3.7 mL/min), and glomerular filtration rate (89 +/- 4 to 110 +/- 4 mL/min) in only 5 patients (responders). No significant changes in these parameters (15 +/- 6 to 11 +/- 4 mu Eq/min, 5.5 +/- 1.0 to 4.2 +/- 1.1 mL/min, and 81 +/- 5 to 79 +/- 6 mL/min, respectively) were observed in the remaining patients (nonresponders). Compared with responders, nonresponders had significantly lower baseline sodium excretion (P less than 0.02), urine flow (P less than 0.05), free water clearance (2.5 +/- 0.9 vs. 6.9 +/- 2.1 mL/min; P less than 0.05), and mean arterial pressure (82 +/- 3 vs. 96 +/- 2 mm Hg; P less than 0.01) and significantly higher plasma renin activity (16.3 +/- 4.9 vs. 1.8 +/- 0.2 ng.mL-1.h-1; P less than 0.05) and aldosterone level (99 +/- 24 vs. 13 +/- 2 ng/dL; P less than 0.05). Atrial natriuretic peptide produced a similar reduction of arterial pressure in both groups. To investigate whether the blunted natriuretic response to atrial natriuretic peptide in nonresponders was caused by their lower arterial pressure, atrial natriuretic peptide was infused in 7 of these patients after increasing their arterial pressure to the levels of responders with nonrepinephrine. The increase in arterial pressure (from 81 +/- 5 to 95 +/- 5 mm Hg), which was not associated with significant changes in plasma renin activity and aldosterone concentration, did not reverse the blunted renal response to atrial natriuretic peptide in any of these patients. These results indicate that cirrhotic patients with blunted renal response to atrial natriuretic peptide are characterized by low arterial pressure, marked overactivity of the renin-aldosterone system, and severe sodium and water retention. Correction of hypotension without increasing effective blood volume does not restore renal insensitivity to atrial natriuretic peptide.

Muscle sympathetic nerve activity and renal responsiveness to atrial natriuretic factor during the development of hepatic ascites

PURPOSE

Sodium retention in cirrhosis has been attributed to an imbalance between vasoconstrictive antinatriuretic forces such as the sympathetic nervous system and vasodilatory natriuretic agents such as atrial natriuretic factor (ANF). With the development of refractory ascites, cirrhotic patients become unresponsive to the natriuretic effect of ANF. Animal data suggest that the sympathetic nervous system plays a key role in mediating the refractoriness to ANF. We therefore studied the relationship between sympathetic nerve activity (SNA) and the natriuretic response to ANF in normal subjects and cirrhotic patients. We also attempted to localize the intrarenal site of refractoriness to ANF by lithium clearance.

PATIENTS AND METHODS

Twenty-six patients with biopsy-proven cirrhosis and seven age- and sex-matched normal volunteers were studied after a week of 20 mmol/day sodium intake and no diuretics. Muscle SNA was recorded from the peroneal nerve (microneurography) and correlated with responsiveness to a 2-hour ANF infusion. Lithium clearance was used as a marker of sodium reabsorption proximal to the intramedullary collecting duct, the main site of ANF action. Plasma norepinephrine, renin, and aldosterone levels were also determined. Patients were categorized into three groups: nine patients free of ascites (by ultrasonography), five ascitic patients who responded to a 2-hour ANF infusion (i.e., had a natriuretic response to ANF above 0.83 mmol/hour), and 12 ascitic patients who did not respond.

RESULTS

Muscle SNA was greatly increased in the ascitic nonresponder patients compared with the normal subjects (64 +/- 4 versus 27 +/- 7 bursts/minute, p less than 0.001), moderately increased in ascitic responders (47 +/- 6 bursts/minute, p less than 0.05), but not significantly increased in nonascitic patients with cirrhosis (34 +/- 5 bursts/minute). SNA was positively correlated with plasma norepinephrine levels (r = 0.69; p less than 0.005) and inversely correlated with peak sodium excretion during the ANF infusion (r = -0.63; p less than 0.001). Plasma renin activity and aldosterone were markedly elevated in ascitic nonresponders, and normal in ascitic responders and nonascitic patients. Lithium clearance was reduced in ascitic patients compared with nonascitic patients, did not change after the ANF infusion, and correlated inversely with SNA (r = -0.61; p less than 0.01).

CONCLUSION

These results support the concept that the sympathetic nervous system is a factor in renal sodium handling in cirrhosis, especially in the initiation of sodium retention and the development of refractory ascites. Refractoriness to ANF might be explained, at least in part, by increased neurally mediated sodium reabsorption proximal to the intramedullary collecting duct, the main site of ANF action.

Enkephalinase (EC 3.4.24.11) inhibitors: protection of endogenous ANF against inactivation and potential therapeutic applications

Atrial natriuretic factor (ANF) is a cardiac hormone exerting potent cardiovascular and renal effects but its poor intestinal absorption and rapid inactivation have prevented so far its therapeutic utilisation. However inhibition of endogenous ANF metabolism progressively emerges as a novel therapeutic approach in cardiovascular and renal disorders. The critical role played by enkephalinase (membrane metalloendopeptidase, EC 3.4.24.11) in ANF inactivation was deduced from the effects of inhibitors. These compounds not only protect partially exogenous ANF from hydrolysis by some tissue preparations in vitro but also, in vivo, they increase the half-life of the exogenous hormone in plasma and, even more markedly, its recovery in intact form in kidney, a major target organ. In addition, enkephalinase inhibitors increase by two- to three-fold the circulating level of endogenous ANF, even when the latter is already markedly elevated, such as in patients with chronic heart failure. Finally, enkephalinase inhibitors induce a series of ANF-like responses such as natriuresis, diuresis or increase in cGMP excretion which are attributable to the hormone. These pharmacological observations, as well as preliminary clinical trials, suggest that enkephalinase inhibitors may represent a novel class of therapeutic agents with potential applications in congestive heart failure, essential hypertension and various sodium-retaining states.