binding of [125I]-angiotensin II to VSMC ( IC50 = 1.1 nM )

Losartan Carboxylic Acid (E-3174) inhibits the specific binding of [125I]-angiotensin II to VSMC with an IC50 of 1.1 nM. In VSMC, the angiotensin II-induced production of inositolphosphates is eliminated by losartan carboxylic acid. With an IC50 of 5 nM, losartan carboxylic acid suppresses the increase in intracellular cytosolic Ca2+ concentration that is brought about by angiotensin II. Losartan Carboxylic Acid is superior to losartan in its ability to inhibit the rise in Egr-1 mRNA brought on by angiotensin II. With an IC50 of 3 nM, losartan carboxylic acid inhibits the angiotensin II-induced cell protein synthesis[1].

Losartan Carboxylic Acid (E-3174) (0.1 mg/kg; i.v. followed by 0.02 mg/kg/h for 5.5 h) produces a pressor response inhibition (87±4%) comparable to that of angiotensin I[3]. Anesthetized dogs with a recent anterior myocardial infarction (8.1±0.4 days) are given intravenous lossartan carboxylic acid injection. One hour after treatment begins, the left circumflex coronary artery is electrolytically injured to cause posterolateral ischemia and thrombotic occlusion[4].

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Losartan, EXP3174 and captopril elevated plasma renin activities and comparably and significantly reduced mean arterial pressure. No significant electrocardiographic or cardiac electrophysiologic effects were noted with any treatment. Incidences of acute posterolateral ischemia-induced lethal arrhythmias were: vehicle, 7/9 (77%); losartan, 6/8 (75%); EXP3174, 2/8 (25%; p < 0.05 vs. vehicle control); captopril, 7/10 (70%). There were no among-group differences in time to onset of acute posterolateral ischemia or underlying anterior infarct size. Conclusions: EXP3174, but not losartan nor captopril, reduced the incidence of lethal ischemic ventricular arrhythmia in this preparation. The antiarrhythmic efficacy of EXP3174 may be due to an attenuation of deleterious effects of local cardiac AII formed during acute myocardial ischemia or, alternatively, a non-AII-related activity specific to EXP3174. These findings suggest that in humans, metabolic conversion of losartan to EXP3174 may afford antiarrhythmic protection[4].

Reseaarchers studied the binding properties of KRH-594, a new selective antagonist of angiotensin II (AII) type 1 (AT1) receptors, to rat liver membranes and to recombinant AT1 and AT2 receptors. Preincubation of rat liver membranes with KRH-594 produced maximal inhibition of [125I]-AII binding when the preincubation time was 1-2 h. Preincubation with KRH-594 for 2 h decreased the B(max) value and increased the Kd value. For human AT1, human AT2, rat AT1A and rat AT1B receptors, the Ki values for KRH-594 were 1.24, 9360, 0.67, and 1.02 nm, respectively. The rank order of K1 values for human AT1 receptors was KRH-594 >> EXP3174 > candesartan = AII. The order of specificities for human AT1 and AT2 receptors was candesartan > EXP3174 > KRH-594. Although a 2-h preincubation of human AT2 receptors with KRH-594 (30 microM) or CGP 42112 (a selective AT2 receptor antagonist; 0.3 nM) inhibited binding of [125I]-AII, the suppression by KRH-594 was not significant. These results indicate that KRH-594 binds potently to AT1 receptors in an insurmountable manner, and that at a very high dose (30 microM) it may also bind to AT2 receptors, but in a surmountable manner[2].

Objective: EXP3174 is a metabolite of losartan (previous name DuP753), which is a non-peptide angiotensin II receptor antagonist. Design: The inhibitory potency of these two antagonists on the angiotensin II-induced responses in vascular smooth muscle cells (VSMC) was investigated. Methods: The effect of angiotensin II on cell growth was determined by [3H]-thymidine incorporation into cell DNA and by cellular protein measurements. Intracellular cytosolic Ca2+ concentration was measured by the fura-2 method. Inositolphosphates were determined by high-performance liquid chromatography after cell labelling with myo-[2-3H]-inositol. The early growth response gene-1 (Egr-1) messenger RNA (mRNA) expression was determined by the Northern blotting method. Binding and displacement studies of the antagonists were performed using [125I]-angiotensin II. Results: An apparent dissociation constant (Kd) of 5.9 nmol/l for [125I]-angiotensin II (maximal binding coefficient 69 fmol/10(6) cells) was found. The specific binding of [125I]-angiotensin II to VSMC was inhibited by losartan, EXP3174 and saralasin with a half-maximal inhibitory concentration (IC50) of 1.0 X 10(-8), 1.1 X 10(-9) and 1.8 X 10(-9) mol/l, respectively. EXP3174 and losartan abolished the angiotensin II-induced formation of inositolphosphates in VSMC. EXP3174 and losartan inhibited the angiotensin II-induced elevation of intracellular cytosolic Ca2+ concentration with an IC50 of 5 X 10(-9) and 5 X 10(-8) mol/l, respectively. EXP3174 was more effective than losartan in blocking the angiotensin II-induced increase in Egr-1 mRNA. EXP3174 and losartan inhibited the angiotensin II-induced cell protein synthesis with an IC50 of 3 X 10(-9) and 4 X 10(-8) mol/l, respectively. Conclusions: These results indicate that EXP3174 is significantly more potent than losartan in blocking angiotensin II-induced cellular responses[1].

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For 48 hours, cells were treated with either 15% FBS or Ang II in the presence or absence of the recommended dosage of losartan. Using the MTT assay, cell proliferation was assessed.

Mongrel dogs of either sex, weighing 15-25 kg
0.1 mg/kg (followed by 0.02 mg/kg/h)
i.v. for 5.5 hours

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1. In order to determine whether the renin-angiotensin system is involved in myocardial ischaemia-reperfusion injury, we investigated and compared the effects on infarct size of two different drugs which interfere with this system, i.e., an angiotensin II (AT1) antagonist, EXP3174, and an angiotensin I-converting enzyme inhibitor (ACEI), enalaprilat in a canine model of ischaemia-reperfusion. 2. EXP3174 (0.1 mg kg-1, i.v. followed by 0.02 mg kg-1 h-1 for 5.5 h) and enalaprilate (0.3 mg kg-1, i.v. followed by 0.06 mg kg-1 h-1 for 5.5 h) were used in doses inducing a similar level of inhibition (87 +/- 4 and 91 +/- 3%, respectively) of the pressor responses to angiotensin I. Control animals received saline. 3. Infarct size and area at risk were quantified by ex vivo dual coronary perfusion with triphenyltetrazolium chloride and monastral blue dye. Regional myocardial blood flows (ischaemic and nonischaemic, endocardial, epicardial) were assessed by the radioactive microsphere technique. 4. Both EXP3174 and enalaprilat induced a decrease in mean arterial blood pressure. However, non significant changes in regional myocardial blood flows, whether ischaemic or nonischaemic, were observed after administration of either the ACEI or the AT1 antagonist. 5. The size of the area at risk was similar in the three groups. By direct comparison, there were no significant differences between infarct sizes in the three groups. Furthermore, there was a close inverse relationship between infarct size and transmural mean collateral blood flow in controls, and none of the treatments altered this correlation. Thus, neither EXP3174 nor enalaprilat limited infarct size. 6. These results indicate that activation of the renin-angiotensin system does not contribute to myocyte death in this canine ischaemia/reperfusion model.[3]

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Intravenous losartan (1 mg/kg + 0.03 mg/kg/min), EXP3174 (0.1 mg/kg + 0.01 mg/kg/min), captopril (1 mg/kg + 0.5 mg/kg/h) or vehicle were infused in anesthetized dogs with recent (8.1 +/- 0.4 days) anterior myocardial infarction. Electrolytic injury of the left circumflex coronary artery to induce thrombotic occlusion and posterolateral ischemia was initiated 1 h after the start of treatment.[4]

Metabolism / Metabolites
Losartan carboxylic acid is a known human metabolite of losartan carboxaldehyde and losartan.

mouse LD50 intraperitoneal 441 mg/kg SENSE ORGANS AND SPECIAL SENSES: MYDRIASIS (PUPILLARY DILATION): EYE; BEHAVIORAL: TREMOR; LUNGS, THORAX, OR RESPIRATION: RESPIRATORY DEPRESSION Kiso to Rinsho. Clinical Report., 28(3959), 1994

[1]. EXP3174, a metabolite of losartan (MK 954, DuP 753) is more potent than losartan in blockingthe angiotensin II-induced responses in vascular smooth muscle cells. J Hypertens. 1993 Feb;11(2):155-62.

[2]. Binding of KRH-594, an antagonist of the angiotensin II type 1 receptor, to cloned human and rat angiotensin II receptors. Fundam Clin Pharmacol. 2002 Aug;16(4):317-23.

[3]. Comparison of the effects of EXP3174, an angiotensin II antagonist and enalaprilat on myocardial infarct size in anaesthetized dogs. Br J Pharmacol. 1993 Nov;110(3):969-74.

[4]. EXP3174, the AII antagonist human metabolite of losartan, but not losartan nor the angiotensin-converting enzyme inhibitor captopril, prevents the development of lethal ischemic ventricular arrhythmias in a canine model of recent myoca.

Losartan carboxylic acid is a biphenylyltetrazole that is losartan with the hydroxymethyl group at position 5 on the imidazole ring replaced with a carboxylic acid. It has a role as a metabolite. It is a biphenylyltetrazole, a member of imidazoles and an organochlorine compound. It is functionally related to a losartan.

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The antiarrhythmic efficacies of the competitive angiotensin II (AII) antagonist losartan, losartan's more potent noncompetitive AII antagonist human metabolite EXP3174 and the angiotensin-converting enzyme inhibitor captopril were assessed in a canine model of recent myocardial infarction. Background: Multiple hemodynamic and electrophysiologic effects of AII may contribute to cardiac electrical instability. In the recent Losartan Heart Failure Study, Evaluation of Losartan in the Elderly (ELITE), a 722-patient trial primarily designed to assess effects on renal function, an unexpected survival benefit was observed with losartan compared with captopril, with the lower mortality using losartan primarily confined to a reduction in sudden cardiac death.[4]

C22H21CLN6O2

436.89

436.14

C, 60.48; H, 4.85; Cl, 8.11; N, 19.24; O, 7.32

124750-92-1

Losartan-d4 (carboxylic acid); 1246820-62-1; Losartan; 114798-26-4; Losartan potassium; 124750-99-8; Losartan carboxylic acid-d4 hydrochloride

108185

White to off-white solid powder

5

2

6

8

31

590

0

ZEUXAIYYDDCIRX-UHFFFAOYSA-N

InChI=1S/C22H21ClN6O2/c1-2-3-8-18-24-20(23)19(22(30)31)29(18)13-14-9-11-15(12-10-14)16-6-4-5-7-17(16)21-25-27-28-26-21/h4-7,9-12H,2-3,8,13H2,1H3,(H,30,31)(H,25,26,27,28)

2-butyl-5-chloro-3-[[4-[2-(2H-tetrazol-5-yl)phenyl]phenyl]methyl]imidazole-4-carboxylic acid

Losartan Carboxylic Acid; EXP 3174; Losartan carboxylic acid; 124750-92-1; EXP-3174; Exp3174; EXP 3174; E-3174; Carboxylosartan; 2-butyl-5-chloro-3-[[4-[2-(2H-tetrazol-5-yl)phenyl]phenyl]methyl]imidazole-4-carboxylic acid; EXP-3174; EXP3174; E3174; E-3174; E 3174

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO: ~87 mg/mL (~199.1 mM)
Ethanol: ~87 mg/mL

Solubility in Formulation 1: ≥ 2.08 mg/mL (4.76 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.08 mg/mL (4.76 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)