BQ-3020 is a linear endothelin (ET) analog that is highly selective for ETB receptors. It displaces [125I] ET-1 binding to ETB receptors in porcine cerebellar membranes with an IC50 value of 0.2 nM [1].
ET-1, a 21-amino acid peptide, is one of known isoforms of endothelin (ET-1, ET-2, ET-3), it has strong vasoconstrictor and mitogenic activity. ETB receptor is one of endothelin receptors (i.e. ETA and ETB). ETB receptor has nearly the same affinity for all endothelin isoforms [2].
BQ-3020 displaced [125I] ET-1 binding to ETB receptors in porcine cerebellar membranes at a concentration 4,700 times lower than that to ETA receptors (selective to ET-1) on aortic vascular smooth muscle cells (IC50: 940 nM) [1].
In eight healthy men aged from 20-28 years, the local response of Sarafotoxin S6c (SFTX6c) (5 pmol/min) or BQ-3020 (50 pmol/min) to intra-arterial or intravenous infusion was assessed. Comparing these studies, there was no significant difference between baseline measurements. All the effects were just in the infused arm. Following intra-arterial infusion, both SFTX6c and BQ-3020 produced vasoconstriction indicated by the reduction in forearm blood flow (-25±7% and -27±7%, respectively). Following intravenous infusion, both SFTX6c and BQ-3020 produced a vein diameter reduction (-30±8% and -16±7%, respectively) [3].
References:
[1]. Ihara M, Saeki T, Fukuroda T, et al. A novel radioligand [125I]BQ-3020 selective for endothelin (ETB) receptors. Life Sci., 1992, 51(6):PL47-52.
[2]. Seo B, Oemar BS, Siebenmann R, et al. Both ETA and ETB receptors mediate contraction to endothelin-1 in human blood vessels. Circulation, 1994, 89(3):1203-8.
[3]. Strachan FE, Crockett TR, Mills NL, et al. Constriction to ETB receptor agonists, BQ-3020 and sarafotoxin S6c, in human resistance and capacitance vessels in vivo. Br J Clin Pharmacol., 2000, 50(1):27-30.