Cardiac autonomic tone during trandolapril-irbesartan low-dose combined therapy in hypertension: a pilot project.

Pharmacological and clinical studies on the effects of angiotensin-converting enzyme (ACE) inhibitors support the idea of a central role played Angiotensin II which is able to cause cardiovascular and renal diseases also independently of its blood pressure elevating effects. The present investigation was aimed at evaluating the effect(s) of three different pharmacological regimens on both blood pressure and sympathetic drive in uncomplicated essential hypertension, by means of blood pressure laboratory measurements and ambulatory monitoring, 24-h heart rate variability and plasma noradrenaline levels. Thus, an ACE-inhibitor monotherapy (trandolapril, 2 mg/day), an AT(1)-receptor antagonist monotherapy (irbesartan, 300 mg/day), their low-dose combination (0.5 mg/day plus 150 mg/day, respectively) and placebo were given, in a randomised, single-blind, crossover fashion for a period of 3 weeks each to 12 mild essential hypertensives. Power spectral analysis (short recordings) and noradrenaline measurements were also performed in the supine position and after a postural challenge (60 degrees head-up tilting test: HUT). The low-dose combination therapy induced the greatest reduction in LF component and in LF/HF ratio, both in the resting and tilted positions, as well as in blood pressure. However, the physiological autonomic response to HUT was maintained. Noradrenaline plasma levels were lower after the combined therapy than after each drug alone. Our data demonstrate that in mild and uncomplicated essential hypertension, the chronic low-dose combination therapy with an ACE-inhibitor and an AT(1)-antagonist is more effective than the recommended full-dose monotherapy with either drug in influencing the autonomic regulation of the heart, suggesting a relative reduction in sympathetic drive both at cardiac and systemic levels.

Agonist-specific regulation of monocyte chemoattractant protein-1 expression by cyclooxygenase metabolites in hepatic stellate cells.

Activated hepatic stellate cells (HSC) regulate the liver "wound-healing" response through expression of chemokines, including monocyte chemoattractant protein-1 (MCP-1), which participate in the formation of the inflammatory infiltrate during liver injury. Cyclooxygenase (COX) catalyzes the conversion of arachidonic acid into prostaglandins, which may contribute to the inflammatory response. In this study, we investigated the effects of COX inhibitors on the expression of MCP-1 in cultured HSC. Pretreatment of HSC with nonspecific COX inhibitors such as indomethacin or ibuprofen markedly reduced the expression of MCP-1 caused by exposure to tumor necrosis factor alpha (TNF-alpha) or interleukin-1alpha (IL-1alpha). NS-398, a specific COX-2 inhibitor, also resulted in a dose-dependent inhibition of MCP-1 gene and protein expression. These effects were dependent on reduced MCP-1 transcription, as established using a reporter plasmid. In contrast, the up-regulation of MCP-1 expression caused by interferon gamma (IFN-gamma) was not sensitive to COX inhibitors. Quiescent HSC did not show detectable expression of COX-2, which became evident after activation in culture, and while TNF-alpha and IL-1alpha markedly increased the expression of COX-2, IFN-gamma did not have any effects. Pretreatment of HSC with the stable cyclic adenosine monophosphate (cAMP) analog, 8-bromo cAMP, reverted the effects of the COX-2 inhibitor, but not of a nuclear factor-kappaB (NF-kappaB) inhibitor, demonstrating that prostaglandins modulate MCP-1 expression via production of cAMP. On the other hand, the action of NF-kappaB inhibitors was negligible in IFN-gamma-stimulated cells. These findings indicate that cross-talk between cytokines and a prostaglandin-cAMP pathway differentially regulates the proinflammatory potential of HSC, contributing to the modulation of liver tissue inflammation.

C-type natriuretic peptide does not affect plasma and urinary adrenomedullin in man.

To investigate whether C-type natriuretic peptide (CNP) at pathophysiological plasma levels stimulates the release of adrenomedullin (ADM) in man, six healthy subjects (three men and three women, mean age 35 +/- 3 years, range 33-40 years) received an intravenous infusion of synthetic human CNP-22 (2 pmol kg-1 min for 2 h), in a single-blind, placebo-controlled, random order, cross-over study, with measurements of the plasma levels of cyclic guanosine monophosphate (cGMP), ADM, renin and atrial natriuretic peptide (ANP), arterial pressure, heart rate, renal blood flow (para-aminohippurate clearance), glomerular filtration rate (creatinine clearance), and the urinary excretion rates of cGMP, ADM and sodium. Infusion of CNP induced increases in its own levels (from 1.17 +/- 0.11 up to 21.13 +/- 1.41 pmol l-1) without modifying the plasma levels of cGMP, ADM, renin and ANP, the urinary excretion rate of ADM and cGMP, renal haemodynamics and sodium excretion. These data indicate that circulating CNP is not involved in the regulation of ADM release, renal haemodynamics and sodium excretion in man.

Different effects of atrial and C-type natriuretic peptide on the urinary excretion of endothelin-1 in man.

1. Following the observation that brain natriuretic peptide enhances the urinary excretion rate of endothelin-1, the relationship between natriuretic peptides and urinary endothelin-1 was further investigated. Six healthy volunteers received, on three different occasions, increasing doses of atrial or C-type natriuretic peptide (0, 2 and 4 pmol.min-1.kg-1 for 1 h each), or placebo.2. Atrial natriuretic peptide caused significant increases in the urinary excretion of cGMP, sodium and endothelin-1, without affecting plasma endothelin-1, renal plasma flow, glomerular filtration rate and urine flow rate. C-type natriuretic peptide did not modify any of these parameters. During atrial natriuretic peptide infusion, urinary endothelin-1 directly correlated with plasma atrial natriuretic peptide, urinary cGMP and sodium excretion.3. These results indicate that enhancement of the urinary excretion of endothelin-1 by natriuretic peptides is dose-dependent and somewhat related to their ability to bind to natriuretic peptide receptors A, activate guanylate cyclase and induce a natriuretic response.

Effects of supplementation with unsaturated fatty acids on plasma and membrane lipid composition and platelet function in patients with cirrhosis and defective aggregation.

BACKGROUND/AIMS: Defective platelet aggregation and reduced platelet production of thromboxane A2, a metabolite of arachidonic acid, are common findings in patients with cirrhosis. We evaluated the effects of dietary supplementation with two combinations of unsaturated fatty acids on platelet function and plasma and membrane fatty acids in patients with liver cirrhosis. METHODS: In a double-blind study, 15 patients with cirrhosis and defective aggregation were randomized to receive a 6-week supplementation with gamma-linolenic and linoleic acid (1 g/day of each fatty acid) or with oleic acid and linoleic acid (groups GLA and OA, respectively). RESULTS: Under baseline conditions, patients showed elevated concentrations of monounsaturated fatty acids and a reduction in polyunsaturated fatty acids. The product/precursor ratios for delta6 and delta5 desaturases, two key enzymes in the pathway leading to arachidonic acid, were significantly reduced in the group of patients. In the GLA group, a significant increase in the levels of dihomo-gamma-linolenic acid (20:3omega6) was observed in plasma and membranes, together with a parallel decrease in the 20:4/20:3omega6 ratio after supplementation. No significant changes were observed in the OA group. The levels of arachidonic acid did not change significantly in either group of patients. Platelet aggregation to collagen was unchanged in the GLA group, but significantly improved in the OA group. CONCLUSIONS: These results show that supplementation with precursors of arachidonic acid is ineffective in elevating plasma or membrane arachidonate levels and does not improve platelet aggregation, suggesting that synthesis of arachidonic acid through the delta5 desaturase cannot be correspondingly activated or that incorporation/retention of the produced fatty acid into lipids is impaired. The increased platelet aggregation in the OA group is likely to be explained by the effect of oleic acid contained in the diet, the effects of which may have been counteracted by the elevation in 20:3omega6, a source of anti-aggregatory prostanoids, in the GLA group.

Effect of some cyclooxygenase inhibitors on the increase in guanosine 3':5'-cyclic monophosphate induced by NO-donors in human whole platelets.

1. The effect of the NSAIDs indomethacin, indoprofen, diclofenac and acetylsalicylic acid on the increase in guanosine 3':5'-cyclic monophosphate (cyclic GMP) induced by nitric oxide-donor agents was tested in human whole platelets and in platelet crude homogenate. 2. In whole platelets, indomethacin reduced the increase in cyclic GMP induced by the nitric oxide-donors (NO-donors) sodium nitroprusside (NaNP) and S-nitroso-N-acetylpenicillamine (SNAP) in a dose-dependent way, its IC50 being 13.7 microM and 15.8 microM, respectively. 3. Of the other cyclooxygenase inhibitors tested, only indoprofen reduced the increase in cyclic GMP induced by both NO-donors in a dose-dependent way (IC50=32.7 microM, NaNP and 25.0 microM, SNAP), while acetylsalicylic acid (up to 1000 microM) and diclofenac (up to 100 microM) were ineffective. 4. However, in platelet crude homogenate neither indomethacin nor indoprofen reduced the cyclic GMP production. 5. Indomethacin (10 microM), indoprofen (30 microM), diclofenac (100 microM) and acetylsalicylic acid (1000 microM) showed a comparable efficacy in inhibiting platelet thromboxane B2 (TXB2) production, suggesting that the inhibitory effect of indomethacin and indoprofen on the increase in cyclic GMP induced by both NO-donors was not mediated by inhibition of cyclooxygenase. 6. In vitro, the NSAIDs analysed did not interfere with nitrite production of SNAP. 7. The unhomogeneous behaviour of NSAIDs on the increase in cyclic GMP induced by NO-donors in whole platelets may contribute to the different pharmacological and toxicological characteristics of the drugs, providing new knowledge on the effect of indomethacin and indoprofen.

Urinary endothelin-1 excretion is enhanced by low-dose infusion of brain natriuretic peptide in normal humans.

To evaluate the functional relationship between cardiac natriuretic peptides and endothelin-1 within the human kidney, we studied the effects exerted by infusion of brain natriuretic peptide on urinary endothelin-1 excretion. We studied twice in a single-blind manner five normal volunteers who received a constant infusion of 5% dextrose (250 mL/h) or human brain natriuretic peptide-32 at a dose of 4 pmol/kg per minute. Blood samples were drawn at intervals for measurement of hematocrit and concentrations of creatinine, electrolytes, brain natriuretic peptide, and endothelin-1. Urine was collected an intervals for measurement of flow rate and concentrations of creatinine, sodium, cGMP, and endothelin-1. Blood pressure and heart rate were measured every 15 minutes. Placebo administration did not change blood pressure, heart rate, or any of the other parameters measured in plasma and urine. As expected, brain natriuretic peptide infusion caused significant increases in its own plasma levels (basal versus peak levels [mean +/- SD], 1.45 +/- 0.20 versus 50.5 +/- 6.0 pmol/L, P < .01), in urinary cGMP (0.75 +/- 0.16 versus 1.92 +/- 0.81 fmol/min, P < .05), and in urinary sodium excretion (140.0 +/- 38.7 versus 624.2 +/- 181.6 mumol/min, P < .01). In addition, it caused an increase in urinary endothelin-1 excretion (4.32 +/- 2.11 versus 19.67 +/- 9.52 fmol/min, P < .05), without modifying plasma endothelin-1, blood pressure, heart rate, creatinine clearance, and urinary flow rate. Our data indicate that brain natriuretic peptide, at plasma levels comparable to those observed in patients with heart failure, causes a significant increase in urinary but not plasma endothelin-1, thus demonstrating a functional link between cardiac natriuretic peptides and renal release of endothelin-1.

Membrane binding sites and non-genomic effects of estrogen in cultured human pre-osteoclastic cells.

Besides functional estrogen receptors, the presence of signalling cell surface binding sites for 17beta-estradiol (17betaE2) has been reported in osteoblast- and osteoclast-like cells, suggesting that 17betaE2 may influence bone remodelling by a dual mechanism of action: to affect gene expression mediated by the nuclear activity of the steroid-receptor complex, and to initiate rapid responses triggered by a signal-generating receptor on the cell surface. Recently, we demonstrated that the human pre-osteoclastic cell line FLG 29.1 bears functional estrogen receptors. In this study we examined FLG 29.1 cells for the presence of cell surface binding sites for 17betaE2, and whether 17betaE2 could elicit cell signalling. Using a cell-impermeant and fluorescent estrogen conjugate, 17beta-estradiol-6-carboxymethyloxime-bovine serum albumin-fluorescein isothiocyanate, we demonstrated the presence of specific plasma membrane binding sites for 17betaE2. Stimulation of FLG 29.1 cells with low (1 nM) and high (1 microM) doses of 17betaE2 induced a prompt and significant (P < 0.05) increase of cellular pH, as measured in single cells using an image analysis system. In addition, both cAMP and cGMP were significantly increased by 17betaE2 with a dose-dependent response. Finally, a rapid increase of intracellular calcium ion concentration [Ca2+] was also induced by 1 nM 17betaE2, as measured in single cells using an image analysis system. Our findings strongly suggest a non-genomic action of 17betaE2 on osteoclast precursors.

Endothelin 1 is overexpressed in human cirrhotic liver and exerts multiple effects on activated hepatic stellate cells.

BACKGROUND & AIMS: Endothelin (ET) 1 could be involved in the regulation of hepatic microcirculation and in the development of portal hypertension. The expression and distribution of ET-1 in normal and cirrhotic liver tissue and its effects on hepatic stellate cells (HSCs), liver-specific pericytes, were investigated. METHODS: ET-1 expression in liver tissue was analyzed using in situ hybridization and immunohistochemistry. Secretion of ET-1 by HSC was evaluated by radioimmunoassay. Changes in intracellular Ca2+ concentration and cell contraction were studied using digital video imaging. Specific binding of ET-1 was evaluated using self- and cross-displacement curves. RESULTS: ET-1 expression was markedly enhanced in cirrhotic liver tissue, where activated HSCs were shown to be major sites of ET-1 synthesis, as confirmed by studies performed on cultured human HSC. ET-1 exerted several biological actions on HSC, including mitogenicity, activation of mitogen-activated protein kinase, and a rapid increase in intracellular Ca2+ coupled with reversible cell contraction. All these effects appeared to be mediated by ETA receptors. Finally, the relative prevalence of ETA and ETB binding sites changed with the progressive phenotypical modulation of HSC. CONCLUSIONS: ET-1 may act as a paracrine and autocrine factor for activated HSC and contribute to the increased resistance to portal flow in cirrhotic liver.

Blunted natriuretic response to low-dose brain natriuretic peptide infusion in nonazotemic cirrhotic patients with ascites and avid sodium retention.

Patients with cirrhosis and ascites have high plasma levels of atrial (ANP) and brain (BNP) natriuretic peptides, two cardiac hormones released by the atria and ventricles, respectively. We evaluated renal hemodynamics, sodium excretion, and intrarenal sodium handling (lithium clearance method) in seven cirrhotic patients with ascites and avid sodium retention before, during, and after the infusion of synthetic human BNP, at the dose of 4 pmol/kg.min for 1 hour, which has been shown to increase renal plasma flow, glomerular filtration rate (GFR), and sodium excretion in healthy subjects without affecting systemic hemodynamics. Plasma BNP levels were 7.31 +/- 0.85 pmol/L in baseline conditions, and increased to 33.60 +/- 2.96 pmol/L at the end of the infusion (P < .01 vs. baseline). Urinary excretion of guanosine 3',5'-cyclic monophosphate (cGMP) also significantly increased during the infusion, indicating stimulation of natriuretic peptide receptors by BNP. BNP administration did not modify renal plasma flow, GFR, sodium excretion or tubular sodium reabsorption to any appreciable extent. Arterial pressure heart rate, plasma norepinephrine, and plasma renin activity (PRA) where also unchanged, whereas plasma aldosterone concentration showed a significant, 35% reduction at the end of the postinfusion period, ruling out the possibility that BNP-induced vasodilation might be responsible for failure of the peptide to induce a natriuretic response. Overactivity of antinatriuretic factors is probably the main determinant of the blunted natriuretic effect of BNP in these patients.

Plasma levels of brain natriuretic peptide in healthy subjects and patients with essential hypertension: response to posture.

1. To examine whether posture-induced changes in central volume affect brain natriuretic peptide secretion, plasma levels of human brain natriuretic peptide-32-like immunoreactivity (hBNP-32-li) were measured by radioimmunoassay in 11 healthy subjects and 20 patients with essential hypertension after 15 min supine, 15 min sitting and 15 min with the legs raised at 60 degrees, together with plasma atrial natriuretic peptide concentration, plasma renin activity and plasma aldosterone concentration. 2. In the supine position, the plasma hBNP-32-li level was 1.57 +/- 0.10 fmol/ml in healthy subjects and significantly higher in hypertensive patients (2.39 +/- 0.13 fmol/ml, P < 0.001). In both groups, plasma hBNP-32-li level significantly (P < 0.001) decreased when sitting (normotensive, 1.22 +/- 0.08 fmol/ml; hypertensive, 1.85 +/- 0.15 fmol/ml, P < 0.001 versus normotensive) and increased again after leg raising (normotensive, 2.13 +/- 0.12 fmol/ml; P < 0.002 versus resting; hypertensive, 2.84 +/- 0.16 fmol/min, P < 0.001 versus resting, P < 0.025 versus normotensive). 3. The plasma atrial natriuretic peptide concentration showed similar behaviour to the plasma hBNP-32-li, whereas plasma renin activity and plasma aldosterone concentration increased during sitting and decreased during leg raising in both healthy subjects and hypertensive patients, who had significantly higher plasma aldosterone levels when supine and sitting.(ABSTRACT TRUNCATED AT 250 WORDS)

Natriuretic hormone receptors and actions on bone endothelial cells.

[125I]Atrial natriuretic peptide (ANP) was used to identify ANP receptors on a clonal line of bovine bone endothelial (BBE) cells. Specific binding of [125I]ANP was saturable and of high affinity. Computer analysis of the equilibrium binding data indicated that the Scatchard plots are best fit by a straight line (Kd = 69.3 +/- 20.9 pM; binding capacity = 37.9 fmol/10(6) cells). The order of potency for competing with [125I]ANP binding was human ANP (hANP) > rat atriopeptin-1 (rAP-1) > porcine brain natriuretic peptide (pBNP) > porcine C-type natriuretic peptide. Affinity cross-linking studies indicated the presence of two major 130- and 70-kilodalton bands that specifically bound to hANP, rAP-1, pBNP, and porcine C-type natriuretic peptide. The binding of natriuretic peptides to BBE cells resulted in an increase in cGMP production and a significant decrease in Na+/K+/Cl- cotransport, without effects on cAMP intracellular accumulation. hANP, rAP-1, and pBNP at 100-nM concentrations, significantly inhibited PTH-induced cAMP production. Treatment with natriuretic hormones was also associated with an increase in 6-keto-prostaglandin F1 alpha levels in the culture medium of BBE cells and a higher cell growth rate. These studies demonstrate that bone endothelial cells bear receptors for natriuretic hormones associated with changes in PTH-induced cAMP production, prostaglandin production, and cell proliferation.

[The determination of myocardial necrosis in unstable angina by the immunoradiometric measurement of circulating myosin]. / Individuazione della necrosi miocardica nell'angina instabile mediante dosaggio immunoradiometrico della miosina circolante.

Ventricular myosin heavy chains serum levels are a new marker of myocardial necrosis. We have studied plasma levels of myosin in 30 patients with unstable angina, 30 patients with acute myocardial infarction and 25 healthy subjects. The myosin peak level was 317 +/- 101 microU/L in angina patients, 2510 +/- 433 microU/L in infarcted patients and 62.3 +/- 17 microU/L in the controls. In both groups, the increase in serum myosin was more marked in those with larger infarction and in those with more severe angina. These data suggest that the measurement of serum myosin can identify the presence of micronecrosis in patients with unstable angina, according to what has been found using other markers of myocellular necrosis.

Thromboxane-receptor blockade increases water diuresis in cirrhotic patients with ascites.

This study was undertaken to investigate the role of increased renal thromboxane (TX) A2 production in modulating renal hemodynamics and sodium and water retention in cirrhotic patients with ascites. In a randomized, double-blind, placebo-controlled, crossover trial, 15 nonazotemic cirrhotic patients with ascites and elevated urinary TXB2 excretion received the thromboxane-receptor antagonist ONO-3708 (3 micrograms.kg-1.min-1) in a 4-hour continuous infusion. Administration of ONO-3708 significantly blocked TXA2 receptors; bleeding time showed a twofold increase (432 +/- 65 vs. 131 +/- 17 seconds; P less than 0.005), and platelet aggregation to U-46619 (an agonist of TXA2 receptors) was abolished in all patients studied. The drug induced a significant increase in free water clearance (3.06 +/- 0.70 vs. 1.72 +/- 0.57 mL/min; P less than 0.001) and diuresis (4.74 +/- 0.79 vs. 3.94 +/- 0.66 mL/min; P less than 0.05) compared with placebo, as well as a significant (14%) increase in renal plasma flow. The increases in both free water clearance and diuresis induced by ONO-3708 were directly related to basal urinary TXB2 excretion. These results suggest a role for renal TXA2 as a modulator of water handling in cirrhotic patients with ascites.

Plasma levels of brain natriuretic peptide in patients with cirrhosis.

Plasma levels of brain natriuretic peptide, a recently identified cardiac hormone with natriuretic activity, were measured in 11 healthy subjects, 13 cirrhotic patients without ascites, 18 nonazotemic cirrhotic patients with ascites and 6 patients with cirrhosis, ascites and functional kidney failure. Plasma levels of brain natriuretic peptide were similar in healthy subjects and cirrhotic patients without ascites (5.56 +/- 0.65 and 7.66 +/- 0.68 fmol/ml, respectively). In contrast, cirrhotic patients with ascites, with and without functional kidney failure, had significantly higher plasma concentrations of brain natriuretic peptide (19.56 +/- 1.37 and 16.00 +/- 1.91 fmol/ml, respectively) than did healthy subjects and patients without ascites (p less than 0.01); no significant difference was found between the two groups of cirrhotic patients with ascites with respect to this parameter. In the whole group of cirrhotic patients included in the study, brain natriuretic peptide level was directly correlated with the degree of impairment of liver and kidney function, plasma renin activity and plasma levels of aldosterone and atrial natriuretic peptide. The results of this study indicate that brain natriuretic peptide is increased in cirrhotic patients with ascites and suggest that sodium retention in cirrhosis is not due to deficiency of this novel cardiac hormone.

Effects of repeated atrial natriuretic peptide bolus injections in cirrhotic patients with refractory ascites.

The renal and hormonal effects of repeated atrial natriuretic peptide (ANP) boli (1 microgram/kg of body weight) were studied in eight cirrhotic patients with refractory ascites. Under basal conditions the patients showed a striking activation of the renin-angiotensin-aldosterone system (plasma renin activity 19.3 +/- 3.0 ng/ml.h, plasma aldosterone concentration 3.87 +/- 0.58 ng/ml) and a tenfold elevation in plasma ANP levels compared to healthy subjects (131.7, range 47.0-288.6, vs. 9.8, range 5.0-15.0, fmol/ml, p less than 0.001). The first ANP injection was followed by a remarkable increase in plasma ANP levels and by a slight increase in urinary cyclic guanosine-monophosphate excretion (from 1050.8 +/- 454.8 to 1446.6 +/- 822.2 pmol/min). A significant reduction of mean blood pressure (MBP) occurred 5 min after the first injection (from 86.7 +/- 7.2 to 79.9 +/- 5.8 mmHg, p less than 0.05), but values gradually returned to the baseline after 30 min. Heart rate (HR) increased 10 min after the first bolus injection (from 83.75 +/- 4.7 to 88.1 +/- 4.6 beats/min) and reached baseline values after 30 min. Similar behaviour of MBP and HR was observed after the second, third and fourth bolus injections. Urinary sodium excretion, urinary flow, glomerular filtration rate, plasma renin activity, and plasma aldosterone concentration did not show any significant modification during ANP administration, nor did these parameters change in the following 12-h recovery period.(ABSTRACT TRUNCATED AT 250 WORDS)