In vitro activity: BQ-123 is a potent and selective antagonist of endothelin A receptor (ETAR) with IC50 of 7.3 nM. Endothelin-1 has been shown to increase neuronal activity and glutaminergic synaptic transmission by endothelin-A receptors (ETAR) in the nucleus tractus solitarius neurons that play an important role in epileptic seizures. Therefore, BQ-123 as an ETAR antagonist might attenuate neuronal excitability and glutaminergic synaptic transmission. BQ123 potentiates acetaminophen induced hypothermia and reduces infarction following focal cerebral ischemia in rats. BQ123 Stimulates Skeletal Muscle Antioxidant Defense via Nrf2 Activation in LPS-Treated Rats. BQ123 reduces pulmonary vascular resistance after surgical intervention for congenital heart disease. BQ123 protects against myocardial and endothelial reperfusion injury. In porcine aortic vascular smooth muscle cells, BQ-123 selectively inhibits ETA-mediated contraction. In rat vascular smooth muscle cells, BQ-123 inhibits endothelin-1-induced phosphoinositide breakdown and DNA synthesis.

Kinase Assay: BQ-123 is a potent and selective antagonist of endothelin A receptor (ETAR) with IC50 of 7.3 nM.

Cell Assay: In the ETA-expressing cells, BQ123 (10-6 M) inhibited endothelin-1 (ET-1) (10-6 M)-induced [Ca2+]i increase by 95%. In rat vascular smooth muscle cells (VSMC), BQ-123 inhibited ET-1 receptor binding, cellular contraction, [Ca2+ ]i mobilization, [3H]thymidine incorporation, MAP kinase activation and MTT reduction induced by ET-1. However, BQ-123 didn’t inhibit angiotensin II (Ang II)- and arginine vasopressin (AVP)-induced increases in MAP kinase activity and [Ca2+]i mobilization