Losartan Carboxylic Acid

EXP-3174, also known as Losartan Carboxylic Acid, is a physiologically active metabolite of losartan, produced by cytochrome P450 isoforms in the liver. Like the parent compound, EXP-3174 is a potent AT1 antagonist (Kis = 0.57 and 0.67 nM for rat and human forms, respectively), producing a depressor response and vasodilatation. When administered intravenously, losartan carboxylic acid is more potent and has a longer duration of action than losartan. However, the metabolite has very low oral bioavailability. (In Vitro) :The specific binding of [125I]-angiotensin II to VSMC is inhibited by Losartan Carboxylic Acid (E-3174) with an IC50 of 1.1 nM. Losartan Carboxylic Acid abolishes the angiotensin II-induced formation of inositolphosphates in VSMC. Losartan Carboxylic Acid inhibits the angiotensin II-induced elevation of intracellular cytosolic Ca2+ concentration with an IC50 of 5 nM. Losartan Carboxylic Acid is more effective than losartan in blocking the angiotensin II-induced increase in Egr-1 mRNA. Losartan Carboxylic Acid inhibits the angiotensin II-induced cell protein synthesis with an IC50 of 3 nM. (In Vivo) :Losartan Carboxylic Acid (E-3174) (0.1 mg/kg; i.v. followed by 0.02 mg/kg/h for 5.5 h) induces a similar level of inhibition (87±4%) of the pressor responses to angiotensin I.Intravenous Losartan Carboxylic Acid (0.1 mg/kg+0.01 mg/kg/min) is 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 is initiated 1 h after the start of treatment.