IRL 2500 is a potent Endothelin receptor antagonist. IRL 2500 shows IC₅₀ values of 1.3 and 94 nM for ET_B and ET_A receptors, respectively. IRL 2500 inhibits ETB receptor-mediated blood pressure increase and renal vascular resistance in rats in vivo^[1]. In Vivo: IRL 2500 (intravenous injection;10 mg/kg) inhibits the initial transient decrease in mean arterial pressure (MAP) induced by the ETB-selective agonist IRL 1620 in rats, IRL 2500 also attenuates the IRL 1620-mediated increase in renal vascular resistance (RVR) in the anesthetized rat^[1].
IRL 2500 (intravenous injection;10 mg/kg) pre-reatment significantly reduces the initial vasodepressor response to endothelin-1 (ET-1) and IRL 1620, however, it is not alters the secondary and sustained pressor response to these agonists^[2].