B027 Assessment of angiotensin II receptor blockade in humans using an in vitro binding assay: Comparison with the in vivo approach

Maillard, Marc; Mazzolai, Lucia; Rossat, Julien; Daven, V.; Nussberger, J; Brunner, H R; Burnier, Michel

doi:10.1016/s0895-7061(97)90870-0

Cited by 2 publications

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“…A separate, preliminary analysis of the same data demonstrated that the results obtained with this in vitro receptor binding assay correlate closely with results obtained in vivo with the administration of exogenous Ang II, 13 particularly when only active treatment phases are considered. This indicates that the in vitro assay is a good alternative method for characterizing Ang II receptor blockade in humans.…”

Section: Discussionsupporting

confidence: 58%

“…12 To further assess Ang II receptor blockade, a standardized, in vitro receptor binding assay was used. 13 In brief, this in vitro binding assay measures the ability of a subject's plasma to displace radiolabeled Ang II bound to AT 1 receptors in a rat smooth muscle cell membrane preparation. Binding is performed at 37°C for 1 hour with 100 g of membrane proteins in 375 L of binding buffer in the presence of 5 fmol of labeled Ang II and 25 L of plasma.…”

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confidence: 99%

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Angiotensin II Receptor Blockade in Normotensive Subjects

et al. 1999

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Abstract-Use of angiotensin (Ang) II AT 1 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% (PϽ0.01 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. (Hypertension. 1999;33:850-855.)Key Words: angiotensin II Ⅲ receptors, angiotensin II Ⅲ human Ⅲ irbesartan Ⅲ losartan Ⅲ valsartan F or the past 15 years, angiotensin-converting enzyme (ACE) inhibitors have been widely used to block the renin-angiotensin system and to treat hypertension and congestive heart failure. Despite their recognized clinical efficacy, ACE inhibitors have some weaknesses. First, ACE is a nonspecific enzyme that uses bradykinin as a substrate in addition to angiotensin I (Ang I). Thus, ACE inhibition results in both Ang I and bradykinin accumulation, the latter being a potential source of side effects such as angioedema. 1,2 The occurrence of cough, the most frequent side effect of ACE inhibitors, has also been attributed to the lack of specificity of ACE inhibition. 1 Second, during long-term ACE inhibition, plasma angiotensin II (Ang II) levels decrease, but some Ang II is still circulating at measurable levels. 3 The reactive rise in plasma renin activity and plasma Ang I levels may account for the persistence of measurable Ang II levels, particularly if ACE activity is not fully inhibited around the clock. More recently, it has also been postulated that besides being generated through the primary ACE pathway, Ang II can be generated through non-ACE pathways that are not affected by ACE inhibitors. 4 To overcome the drawbacks of ACE inhibitors, substantial effort has been put into development of new compounds that block the renin-angiotens...

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Section: Discussionsupporting

confidence: 58%

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confidence: 99%

Angiotensin II Receptor Blockade in Normotensive Subjects

et al. 1999

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“…The membranes were obtained according to a method published previously (Maillard et al, 1998). For each experiment, an aliquot of membranes was thawed and centrifuged, and the pellet was resuspended in a 50 mM Tris-HCl, pH 7.2, containing 5 mM MgCl 2 binding buffer to obtain a final concentration of 1 mg of protein/ml.…”

Section: Radioligand Binding Studiesmentioning

confidence: 99%

“…The degree of AT1 receptor blockade induced in rats treated by telmisartan was also measured ex vivo using the standardized radio-receptor assay described previously (Maillard et al, 1998(Maillard et al, , 2000a(Maillard et al, , 2002. To compare the activity of different doses in different rats, the results were normalized and expressed as (B X Ϫ B 0 )/(B RP Ϫ B 0 ), where B X is the residual activity in the presence of the plasma X, B 0 the nonspecific binding, and B RP is the residual activity in the presence of the reference plasma.…”

Section: In Vivo Studiesmentioning

confidence: 99%

In Vitro and in Vivo Characterization of the Activity of Telmisartan: An Insurmountable Angiotensin II Receptor Antagonist

Maillard¹,

Perregaux²,

Centeno³

et al. 2002

J Pharmacol Exp Ther

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In vitro studies have shown that telmisartan is an insurmountable angiotensin II subtype-1 (AT1) receptor antagonist. Herein, the molecular basis of this insurmountable antagonism has been investigated in vitro, and the effect of telmisartan has been compared in vivo with that of irbesartan and candesartan. Association and dissociation kinetics of telmisartan to AT1 receptors have been characterized in vitro on rat vascular smooth muscle cells (RVSMC) expressing solely the AT1 receptor subtype. In a second set of experiments, the antagonistic efficacy of single intravenous doses (0.1, 0.3, and 1 mg/kg) of telmisartan was compared with that of irbesartan (0.3, 1.0, 3.0, and 10.0 mg/kg) and candesartan (0.3 and 1 mg/kg) in conscious, normotensive, male Wistar rats. The results show that the specific binding of [ 3 H]telmisartan to the surface of living RVSMC is saturable and increases quickly to reach equilibrium within 1 h. Telmisartan dissociates very slowly from the receptor with a dissociation half-life (t 1/2 ) of 75 min, which is comparable with candesartan and almost 5 times slower than angiotensin II (AngII). In vivo, telmisartan blunts the blood pressure response to exogenous AngII dose dependently. The blockade is long lasting and remains significant at 24 h at doses Ͼ0.1 mg/kg. Ex vivo assessment of the AT1 receptor blockade using an in vitro AngII receptor binding assay shows similar results. When administered intravenously in rats, telmisartan is 10-fold more potent than irbesartan and comparable to candesartan. Taken together, our in vitro data show that the insurmountable antagonism of telmisartan is due at least in part to its very slow dissociation from AT1 receptors.

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B027 Assessment of angiotensin II receptor blockade in humans using an in vitro binding assay: Comparison with the in vivo approach

Cited by 2 publications

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Angiotensin II Receptor Blockade in Normotensive Subjects

Angiotensin II Receptor Blockade in Normotensive Subjects

In Vitro and in Vivo Characterization of the Activity of Telmisartan: An Insurmountable Angiotensin II Receptor Antagonist

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