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H R Brunner

Publications and source records attributed to H R Brunner.

At least 19 recordsLinked to original sources
PubMed2000

Angiotensin II receptor antagonists.

Blockade of the renin-angiotensin system began as a way of studying the pathogenesis of cardiovascular disease with specific pharmacological probes. Oral activity, achieved by shortening the original peptide structures, transformed the probes into therapeutic agents, the angiotensin-converting enzyme (ACE) inhibitors. However, ACE is a non-specific target for blocking the renin-angiotensin enzymatic cascade. The availability of orally active drugs turned ACE inhibition into a therapeutic breakthrough but more specific blockade always seemed desirable. This goal has now been achieved with the orally active angiotensin II receptor antagonists; six are on the market and more are under development. This new class of drugs is equal in efficacy to ACE inhibitors, at least in hypertensive patients. Trials now underway will demonstrate whether angiotensin II receptor antagonists can prevent target-organ damage and reduce cardiovascular morbidity and mortality. If they do, these compounds might one day replace ACE inhibitors.

Angiotensin Receptor Antagonists↗
PubMed2000

Neuropeptide Y (NPY) potentiates phenylephrine-induced mitogen-activated protein kinase activation in primary cardiomyocytes via NPY Y5 receptors.

Neuropeptide Y (NPY) has been shown to participate in the cardiovascular response mediated by the sympathetic system. In this report, we investigate the growth factor properties of NPY on cardiac myocytes. Mitogen-activated protein kinases (MAPK) are key signaling molecules in the transduction of trophic signals. Therefore, the role of NPY in inducing MAPK activation was studied in mouse neonatal cardiomyocytes. Exposure of neonatal cardiomyocytes to either NPY, phenylephrine, or angiotensin II induces a rapid phosphorylation of the extracellular responsive kinase, the c-jun N-terminal kinase, and the p38 kinase as well as an activation of protein kinase C (PKC). Moreover, NPY potentiates phenylephrine-induced MAPK and PKC stimulation. In contrast, NPY has no synergistic effect on angiotensin II-stimulated MAPK phosphorylation or PKC activity. NPY effects are pertussis toxin-sensitive and calcium-independent and are mediated by NPY Y5 receptors. Taken together, these results suggest that NPY, via G(i) protein-coupled NPY Y5 receptors, could participate in the development of cardiac hypertrophy during chronic sympathetic stimulation by potentiating alpha-adrenergic signals.

Angiotensin II↗
PubMed2000

Unidirectional and oscillatory shear stress differentially modulate NOS III gene expression.

Atherosclerotic plaques preferentially develop in regions exposed to a low mean shear stress and cyclic reversal of flow direction (oscillatory flow). This contrasts with plaque-free zones where endothelial cells are exposed to unidirectional flow. Previous works from our laboratory using a unique experimental flow system demonstrated the existence of a differential regulation of endothelial nitric oxide synthase (NOS III) gene expression by unidirectional and oscillatory flow patterns. We further studied the possible mechanisms responsible for selective unresponsiveness of NOS III gene regulation to oscillatory flow. The results obtained demonstrate that (i) induction of the activity of the 1600-base-pair NOS III gene promoter by unidirectional and oscillatory shear stress is modulated by similar mechanisms that involve NF-kappaB activation, but do not involve Ras-dependent MAP kinase activation, and (ii) the lack of induction of NOS III gene regulation by oscillatory shear stress can be attributed to the activation of a yet unidentified negative cis-acting element present in the NOS III gene.

Base Sequence↗
PubMed2000

Bioavailability of repeated oral administration of MDL 100,240, a dual inhibitor of angiotensin-converting enzyme and neutral endopeptidase in healthy volunteers.

BACKGROUND: MDL 100,240 (pyrido[2,1-a] [2]benzazepine-4-carboxylic acid,7-[[2-(acetylthio)-1-oxo-3-phenylpropyl]amino]-1,2,3,4,6,7,8, 12b-octahydro-6-oxo, [4S-[4alpha,7alpha(R(*)),12bbeta]]-) is a molecule possessing an inhibiting ability on both angiotensin converting enzyme (ACE) and neutral endopeptidase, the enzyme responsible for atrial natriuretic peptide (ANP) degradation. Such a dual mechanism of action presents a potential clinical interest for the treatment of hypertension and congestive heart failure. OBJECTIVES: To evaluate the bioavailability of MDL 100,240 and its accumulation over repeated oral administration, using ACE inhibition as a surrogate for plasma drug level and determining its profile after oral and i.v. administration. METHODS: First, in an open, one-period, single-dose study, the ACE inhibition profile was characterised following a 12.5 mg MDL 100,240 i.v. infusion. Second, in a three-group, parallel, randomised, double-blind study, each group of four subjects received q.d., over 8 days, 2.5, 10 or 20 mg of MDL 100,240 orally. The ACE inhibition profile was determined on day 1 and day 8. Trough plasma ACE was measured on days 2, 3 and 4. The recovery of ACE activity was monitored up to 72 h after the last dose of MDL 100,240. RESULTS: ACE inhibition profile was similar on day 1 and day 8, and trough inhibition remained unchanged after the 8 days of treatment with 10 mg or 20 mg. Following repeated 2.5-mg ingestion, trough inhibition increased from 33% to 44% after the eighth dose. The oral bioavailability of MDL 100,240 was estimated at 85%, not statistically different from 100%. The accumulation ratio at steady state was estimated at 112%. Expressing the accumulation ratio in terms of half-life, a t(1/2) of 0.31 days or 7. 5 h was estimated. CONCLUSION: MDL 100,240 (oral solution) has a good bioavailability, as estimated by ACE inhibition, and no drug accumulation seems to occur over 8 days with the 10-mg and 20-mg doses, but a slight rise in the trough level is observed with the 2. 5-mg dose.

Administration, Oral↗
PubMed2000

Cardiac hypertrophy depends upon sleep blood pressure: a study in rats.

OBJECTIVE: The objective of this study was to determine whether cardiac hypertrophy in hypertensive rats could be reduced and normalized by intermittent reduction of blood pressure, and to determine whether left ventricular hypertrophy was related to 24 h workload or peak blood pressure responses. METHODS: Hypertension was created by the application of a 0.20 mm clip to the left renal artery. Blood pressure response was monitored using a telemetry system (Data Science International). Blood pressure was reduced for varying periods of the day by giving different doses of captopril in the drinking water or by intra-peritoneal administration. Cardiac size was measured by weighing the ventricles and factoring by the body weight to obtain a cardiac index. RESULTS: Captopril 75 mg/kg per day and 25 mg/kg per day in the drinking water administered between 1800 and 2000 h lowered the 24 h blood pressure more than captopril 15 mg/kg per day or 5 mg/kg per day intra-peritoneally given at 0800 h. Captopril 75 mg/kg per day and captopril 15 mg/kg per day (intra-peritoneal) caused regression of cardiac hypertrophy whereas the other doses had no effect The best predictor of the cardiac hypertrophy response was the blood pressure between 0800 and 1200 h (i.e. the sleeping blood pressure). Twenty-four hour cardiac work did not correlate with the response. CONCLUSION: Cardiac hypertrophy can be reduced by intermittent treatment of elevated blood pressure. It is also caused by intermittent elevation of blood pressure. It appears that the crucial factor is when these alterations in blood pressure take place. An elevated blood pressure during the sleeping hours causes left ventricular hypertrophy, whereas a normal blood pressure during the sleeping hours allows reduction. It is suggested that acute wall stress is the signal to initiate the events that lead to cardiac hypertrophy but this only occurs if the hormonal milieu is appropriate.

Animals↗
PubMed2000

Pharmacologic profile of UR-7247, an orally active angiotensin II AT1 receptor antagonist, in healthy volunteers. p6.

This study was conducted to assess the pharmacologic properties of the new orally active angiotensin II subtype I (AT1) antagonist UR-7247, a product with a half-life >100 h in humans. The experiment was designed as an open-label, single-dose administration study with four parallel groups of four healthy men receiving increasing single oral doses (2.5, 5, and 10 mg) of UR-7247 or losartan, 100 mg. Angiotensin II receptor blockade was investigated < or =96 h after drug intake, with three independent methods [i.e., the inhibition of blood pressure (BP) response to exogenous Ang II, an in vitro Ang II-receptor assay (RRA), and the reactive increase in plasma angiotensin II. Plasma drug levels also were measured. The degree of blockade observed in vivo was statistically significant < or = 96 h with all UR-7247 doses for diastolic BP (p < 0.05) and < or =48 h for systolic BP. The maximal inhibition achieved with 10 mg UR-7247 was measured 6-24 h after drug intake and reached 54 +/- 17% and 48 +/- 20% for diastolic and systolic responses, respectively. Losartan, 100 mg, induced a greater short-term AT1-receptor blockade than 2.5- and 5.0-mg doses of UR-7247 (p < 0.001 for diastolic BP), but the UR-7247 effect was longer lasting. In vivo, no significant difference was observed between 10 mg UR-7247 and 100 mg losartan 4 h after drug intake, but in vitro, the blockade achieved with 100 mg losartan was higher than that seen with UR-7247. Finally, the results confirm that UR-7247 has a very long plasma elimination half-life, which may be due to a high but also tight binding to protein binding sites. In conclusion, UR-7247 is a long-lasting, well-tolerated AT1 receptor in healthy subjects.

Administration, Oral↗
PubMed2000

Increased cardiac angiotensin II levels induce right and left ventricular hypertrophy in normotensive mice.

Angiotensin II is a potent arterial vasoconstrictor and induces hypertension. Angiotensin II also exerts a trophic effect on cardiomyocytes in vitro. The goals of the present study were to document an in vivo increase in cardiac angiotensins in the absence of elevated plasma levels or hypertension and to investigate prevention or regression of ventricular hypertrophy by renin-angiotensin system blockade. We demonstrate that high cardiac angiotensin II is directly responsible for right and left ventricular hypertrophy. We used transgenic mice overexpressing angiotensinogen in cardiomyocytes characterized by cardiac hypertrophy without fibrosis and normal blood pressure. Angiotensin-converting enzyme inhibition and angiotensin II type 1 receptor blockade prevent or normalize ventricular hypertrophy. Surprisingly, in control mice, receptor blockade decreases tissue angiotensin II despite increased plasma levels. This suggests that angiotensin II may be protected from metabolization by binding to its receptor. Blocking of the angiotensin II type 1 receptor rather than enhanced stimulation of the angiotensin II type 2 receptor may prevent remodeling and account for the beneficial effects of angiotensin antagonists.

Angiotensin II↗
PubMed2000

Blood pressure and renal haemodynamic response to salt during the normal menstrual cycle.

The purpose of the present study was to evaluate prospectively blood pressure and the renal haemodynamic response to salt during the normal menstrual cycle. A total of 35 healthy normotensive young women not on oral contraceptives were enrolled; 17 were studied in the follicular phase and 18 in the luteal phase of the menstrual cycle. The women in each group were then randomly allocated to receive a low-sodium (40 mmol/day) or a high-sodium (250 mmol/day) diet for a 7-day period in two consecutive menstrual cycles. At the end of each dietary period, 24 h ambulatory blood pressure, urinary sodium excretion, plasma renin activity, plasma catecholamine levels and renal haemodynamics were measured. Our results show that the blood pressure response to salt is comparable during the luteal and the follicular phases of the normal menstrual cycle and is characterized by a salt-resistant pattern. In the kidney, effective renal plasma flow was significantly greater and the filtration fraction lower (P<0.05) after salt loading in women studied in the luteal phase compared with women investigated in the follicular phase. This study thus demonstrates that the female hormone status does not affect the blood pressure response to sodium in young normotensive women. However, in contrast with systemic haemodynamics, the renal response to salt varies during the normal menstrual cycle, suggesting that female sex hormones play a role (direct or indirect) in the regulation of renal haemodynamics.

Adult↗
PubMed1999

Coronary and peripheral artery remodeling in patients undergoing PTCA: An intracoronary and transcutaneous ultrasound study.

The aim of this study was to assess the relationship between the plaque burden of nonstenotic coronary artery segments and the wall thickness of peripheral arteries using intracoronary and transcutaneous ultrasound imaging, respectively. Intracoronary ultrasound (CVIS, 3.5 Fr) was performed in 27 patients undergoing percutaneous transluminal coronary angioplasty. Carotid arteries were imaged by B-mode ultrasound with semiautomatic edge detection and radial arteries by high resolution A-mode echotracking (NIUS 2). Quantitative measurements included coronary artery intima-media cross-sectional area (IM(CSA)) and cross-sectional narrowing (CSN), as well as intima-media thickness (IMT) and lumen radius (r) of the common carotid and the radial arteries. Intima-media thickness was increased in coronary, carotid, and radial arteries. Coronary arteries had an IM(CSA) of 7.7 +/- 2.5 mm(2) and a CSN of 24% +/- 8%. Despite this moderate plaque burden, lumen area was preserved (12.3 +/- 4.2 mm(2)) because of compensatory enlargement of coronary arteries. Right and left carotid and right radial arteries had an IMT of 575 +/- 78 microm, 570 +/- 129 microm, and 328 +/- 61 microm, respectively. There was no correlation between coronary IM(CSA) and carotid IMT (r = 0.07) or radial IMT (r = 0.02), and there was no correlation between coronary CSN and carotid IMT/r (r = 0.12), or radial IMT/r (r = 0.25). In conclusion, in these patients with symptomatic ischemic disease no relationship between IMT of the coronary arteries and IMT of carotid or radial arteries was found. Although increasingly popular, IMT of peripheral arteries may be of limited value as surrogate marker for the severity of coronary artery disease. Cathet. Cardiovasc. Intervent. 48:12-17, 1999.

Adult↗
PubMed1999

Pharmacokinetic and pharmacodynamic effects of YM087, a combined V1/V2 vasopressin receptor antagonist in normal subjects.

OBJECTIVE: The pharmacokinetic and pharmacodynamic properties of YM087, (4'-[(2-methyl-1,4,5,6- tetrahydroimidazo[4,5-d][1]benzazepin-6-yl)-carbonyl]-2-p henylbenzanilide monohydrochloride), a new orally active, dual V1/V2 receptor antagonist were characterised in healthy normotensive subjects. METHODS: Six subjects were randomly allocated to receive, at 1-week intervals, a single oral dose of 60 mg YM087 and a single i.v. dose of 50 mg YM087 in an open-label, crossover study. RESULTS: YM087 had an oral bioavailability of 44% and a short half-life. Upon oral and i.v. administration of YM087, a significant sevenfold increase in urine flow rate and a fall in urinary osmolality (from 600 mosmol/l to less than 100-mosmol/l) were observed with a peak effect 2 h after drug intake suggesting effective vasopressin V2 receptor blockade. Simultaneously, significant increases in plasma osmolality (from 283 +/- 1.3 mosmol/l to 288 +/- 1.0 mosmol/l after i.v. and from 283 +/- 2.1 mosmol/l to 289 +/- 1.7-mosmol/l after oral administration) and vasopressin levels (from 1.5 +/- 0.3 pg/ml to 3.7 +/- 0.6 pg/ml after i.v. and from 0.9 +/- 0.1 pg/ml to 3.9 +/- 0.7 pg/ml after oral administration) were found. When administered i.v., YM087 inhibited the vasopressin-induced skin vasoconstriction, suggesting a blockade of V1 receptors. However, the YM087-induced antagonism of V1 receptors was less pronounced than V2 receptor blockade. CONCLUSION: These data show that YM087 is an effective dual V1/V2 receptor antagonist in man.

Administration, Oral↗
PubMed1999

Renal effects of selective cyclooxygenase-2 inhibition in normotensive salt-depleted subjects.

PURPOSE: To compare the renal hemodynamic and tubular effects of celecoxib, a selective inhibitor of cyclooxygenase-2 (COX-2) to those of naproxen, a nonselective inhibitor of cyclooxygenases in salt-depleted subjects. METHODS AND SUBJECTS: Forty subjects were randomized into four parallel groups to receive 200 mg celecoxib twice a day, 400 mg celecoxib twice a day, 500 mg naproxen twice a day, or a placebo for 7 days according to a double-blind study design. Blood pressure, renal hemodynamics, and urinary water and electrolyte excretion were measured before and for 3 hours after drug intake on days 1 and 7. RESULTS: Celecoxib had no effect on systemic blood pressure, but short-term transient decreases in renal blood flow and glomerular filtration rate were found with the highest dose of 400 mg on day 1. On the first day, both celecoxib and naproxen decreased urine output (P < .05) and sodium, lithium, and potassium excretion (P < .01). On day 7, similar effects on water and sodium excretion were observed. During repeated administration, a significant sodium retention occurred during the first 3 days. CONCLUSION: In salt-depleted subjects, selective inhibition of COX-2 causes sodium and potassium retention. This suggests that an increased selectivity for COX-2 does not spare the kidney, at least during salt depletion.

Adult↗
PubMed1999

Assessment of angiotensin II receptor blockade in humans using a standardized angiotensin II receptor-binding assay.

An in vitro angiotensin II (AngII) receptor-binding assay was developed to monitor the degree of receptor blockade in standardized conditions. This in vitro method was validated by comparing its results with those obtained in vivo with the injection of exogenous AngII and the measurement of the AngII-induced changes in systolic blood pressure. For this purpose, 12 normotensive subjects were enrolled in a double-blind, four-way cross-over study comparing the AngII receptor blockade induced by a single oral dose of losartan (50 mg), valsartan (80 mg), irbesartan (150 mg), and placebo. A significant linear relationship between the two methods was found (r = 0.723, n = 191, P<.001). However, there exists a wide scatter of the in vivo data in the absence of active AngII receptor blockade. Thus, the relationship between the two methods is markedly improved (r = 0.87, n = 47, P<.001) when only measurements done 4 h after administration of the drugs are considered (maximal antagonist activity observed in vivo) suggesting that the two methods are equally effective in assessing the degree of AT-1 receptor blockade, but with a greatly reduced variability in the in vitro assay. In addition, the pharmacokinetic/pharmacodynamic analysis performed with the three antagonists suggest that the AT-1 receptor-binding assay works as a bioassay that integrates the antagonistic property of all active drug components of the plasma. This standardized in vitro-binding assay represents a simple, reproducible, and precise tool to characterize the pharmacodynamic profile of AngII receptor antagonists in humans.

Angiotensin II↗
PubMed1999

Evaluation of noninvasive blood pressure recording by photoplethysmography in clinical studies using angiotensin challenges.

AIMS: Continuous noninvasive blood pressure measurement by photoplethysmography has been regularly used in the experimental paradigm of angiotensin challenges, applied to the phase I clinical testing of angiotensin-converting enzyme inhibitors and angiotensin receptor antagonists. This work aims to evaluate the performance of this measurement method, in terms of reliability, reproducibility and dependence on technical settings. METHODS: Data have been gathered from 13 clinical studies on antihypertensive drugs, using the Finapres device for measuring the response to exogenous angiotensin challenges. The agreement between simultaneous recordings at different fingers and the influence of the reading method are assessed. A literature review addresses the question of the concordance between results obtained noninvasively and through arterial cannulation. RESULTS: The relative precision of blood pressure monitoring by photoplethysmography allows reproducible determination of angiotensin-induced blood pressure peaks (agreement limits for systolic and diastolic peaks: 12 and 6 mmHg respectively). The reading method influences the results to a similar extent. As compared with blood pressure measured intra-arterially, the difference is usually within limits of clinical acceptability. CONCLUSIONS: In the context of phase I studies using the angiotensin challenges methodology, the reliability and reproducibility of noninvasive blood pressure measurement appear satisfactory, despite the technical limitations of this method. The impact of selected changes in the settings and reading methods is limited.

Angiotensin II↗
PubMed1999

Evaluation of the angiotensin challenge methodology for assessing the pharmacodynamic profile of antihypertensive drugs acting on the renin-angiotensin system.

AIMS: The performance of the experimental paradigm of angiotensin challenges with continuous non-invasive blood pressure measurement was evaluated. Angiotensin dose-response relationships were characterized, along with the influence of clinical covariates. The stability of angiotensin-induced peaks and the variability of the angiotensin doses were assessed. Finally, the predictive value of studies based on angiotensin challenges to determine drug doses effective in therapeutics was evaluated. METHODS: The data were gathered from 13 clinical studies on nine angiotensin II receptor antagonists, one ACE inhibitor and one dual ACE-NEP inhibitor, using Finapres for measuring the response to exogenous angiotensin challenges. Modelling of angiotensin dose-response curves and determination of the inter and intrasubject variability were performed by nonlinear regression (NONMEM). The different sources of variations in angiotensin I and II doses and angiotensin-induced peaks were evaluated by analyses of variance. The dose of ACE inhibitors and angiotensin II receptor antagonists inhibiting blood pressure increase by at least 75%, as measured by this method, was chosen for comparison with the labelled starting dose. RESULTS: Angiotensin challenges exhibited a clear dose-response relationship which can be characterized both by an Emax or a log linear model. The log linear model gave an average systolic/diastolic response of 24+/-6/20+/-5 mmHg for a unit dose of 1 microgram of angiotensin II equivalents, and an increase of 6/6 mmHg for each doubling of the dose. The angiotensin ED50 calculated values were 0.67 microgram for systolic and 0.84 microgram for diastolic blood pressure. The angiotensin doses for eliciting a given response and the angiotensin induced peaks were fairly constant between period and subject, but vary significantly between studies. Based on an inhibition of blood pressure by 75%, the agreement was good between the doses of ACE inhibitors and angiotensin receptor antagonists predicted from studies using the methodology of angiotensin challenges and the doses shown to be clinically efficacious, in spite of high intersubject and intrasubject variabilities. CONCLUSIONS: This experimental method represents a valid surrogate for the therapeutic target and a useful tool for the pharmacokinetic and pharmacodynamic profiling of drugs acting on the renin-angiotensin system.

Angiotensin II↗
PubMed1999

Effects of a dual inhibitor of angiotensin converting enzyme and neutral endopeptidase, MDL 100,240, on endocrine and renal functions in healthy volunteers.

OBJECTIVE: To investigate the endocrine and renal effects of the dual inhibitor of angiotensin converting enzyme and neutral endopeptidase, MDL 100,240. DESIGN: A randomized, placebo-controlled, crossover study was performed in 12 healthy volunteers. METHODS: MDL 100,240 was administered intravenously over 20 min at single doses of 6.25 and 25 mg in subjects with a sodium intake of 280 (n = 6) or 80 (n = 6) mmol/day. Measurements were taken of supine and standing blood pressure, plasma angiotensin converting enzyme activity, angiotensin II, atrial natriuretic peptide, urinary atrial natriuretic peptide and cyclic GMP excretion, effective renal plasma flow and the glomerular filtration rate as p-aminohippurate and inulin clearances, electrolytes and segmental tubular function by endogenous lithium clearance. RESULTS: Supine systolic blood pressure was consistently decreased by MDL 100,240, particularly after the high dose and during the low-salt intake. Diastolic blood pressure and heart rate did not change. Plasma angiotensin converting enzyme activity decreased rapidly and dose-dependently. In both the high- and the low-salt treatment groups, plasma angiotensin II levels fell and renin activity rose accordingly, while plasma atrial natriuretic peptide levels remained unchanged. In contrast, urinary atrial natriuretic peptide excretion increased dose-dependently under both diets, as did urinary cyclic GMP excretion. Effective renal plasma flow and the glomerular filtration rate did not change. The urinary flow rate increased markedly during the first 2 h following administration of either dose of MDL 100,240 (P < 0.001) and, similarly, sodium excretion tended to increase from 0 to 4 h after the dose (P = 0.07). Potassium excretion remained stable. Proximal and distal fractional sodium reabsorption were not significantly altered by the treatment. Uric acid excretion was increased. The safety and clinical tolerance of MDL 100,240 were good. CONCLUSIONS: The increased fall in blood pressure in normal volunteers together with the preservation of renal hemodynamics and the increased urinary volume, atrial natriuretic peptide and cyclic GMP excretion distinguish MDL 100,240 as a double-enzyme inhibitor from inhibitors of the angiotensin converting enzyme alone. The differences appear to be due, at least in part, to increased renal exposure to atrial natriuretic peptide following neutral endopeptidase blockade.

Adult↗
PubMed1999

Aortic connexin43 is decreased during hypertension induced by inhibition of nitric oxide synthase.

Connexin43 (Cx43), the predominant gap junction protein in vessels and heart, is involved in the control of cell-to-cell communication and is thought to modulate the contractility of the vascular wall and the electrical coupling of cardiac myocytes. We have investigated the effects of arterial hypertension induced by inhibition of nitric oxide synthase on the expression of Cx43 in aorta and heart as well as on the distensibility of the carotid artery. Administration of 0.4 g/L NG-nitro-L-arginine methyl ester (L-NAME) to rats in their drinking water for 4 weeks increased intra-arterial mean blood pressure, wall thickness of aorta and carotid artery (25%), and heart weight (17%). Analysis of heart mRNA demonstrated increased expression of the fetal skeletal alpha-actin and of atrial natriuretic peptide but not of Cx43. In contrast, Cx43 mRNA and protein were decreased by 50% in the aortas of L-NAME-treated rats that did not show increased carotid distensibility. Because these data contrasted with those obtained in the 2-kidney, 1 clip model of rat hypertension, which is characterized by increased arterial distensibility and Cx43 expression in aorta, we investigated by Western blot analysis the posttranslational modifications of Cx43. We found that Cx43 was more phosphorylated in the aorta of 2-kidney, 1 clip rats than in that of L-NAME or control rats, which indicated a differential regulation of Cx43 in different models of hypertension. The data suggest that the cell-to-cell communication mediated by Cx43 channels may help regulate the elasticity of the vascular wall.

Animals↗
PubMed1999

Angiotensin II receptor blockade in normotensive subjects: A direct comparison of three AT1 receptor antagonists.

Use of angiotensin (Ang) II AT1 receptor antagonists for treatment of hypertension is rapidly increasing, yet direct comparisons of the relative efficacy of antagonists to block the renin-angiotensin system in humans are lacking. In this study, the Ang II receptor blockade induced by the recommended starting dose of 3 antagonists was evaluated in normotensive subjects in a double-blind, placebo-controlled, randomized, 4-way crossover study. At 1-week intervals, 12 subjects received a single dose of losartan (50 mg), valsartan (80 mg), irbesartan (150 mg), or placebo. Blockade of the renin-angiotensin system was assessed before and 4, 24, and 30 hours after drug intake by 3 independent methods: inhibition of the blood pressure response to exogenous Ang II, in vitro Ang II receptor assay, and reactive changes in plasma Ang II levels. At 4 hours, losartan blocked 43% of the Ang II-induced systolic blood pressure increase; valsartan, 51%; and irbesartan, 88% (P<0.01 between drugs). The effect of each drug declined with time. At 24 hours, a residual effect was found with all 3 drugs, but at 30 hours, only irbesartan induced a marked, significant blockade versus placebo. Similar results were obtained when Ang II receptor blockade was assessed with an in vitro receptor assay and by the reactive rise in plasma Ang II levels. This study thus demonstrates that the first administration of the recommended starting dose of irbesartan induces a greater and longer lasting Ang II receptor blockade than that of valsartan and losartan in normotensive subjects.

Adult↗