BQ-3020 ammonium is a selective endothelin receptor ( ET B receptor ) agonist. BQ-3020 ammonium inhibits [ 125 I] ET-1 binding to ET B receptors, with an IC 50 value of 0.2 nM. BQ-3020 ammonium elicits vasoconstriction in the rabbit pulmonary artery. BQ-3020 ammonium makes relaxation of the pig urinary bladder neck and can be used for cardiovascular disease research..