Iberiotoxin

Iberiotoxin is a toxin isolated from Buthus tamulus scorpion venom. Iberiotoxin is a selective high conductance high conductance Ca²⁺-activated K⁺ channel inhibitor with a K_d of ~1 nM. Iberiotoxin does not block other types of voltage-dependent ion channels^[1][2][3]. IC50 & Target:Kd: 1 nM (Ca²⁺-activated K⁺ channel)^[1][3] In Vitro: Iberiotoxin reversibly blocks Ca2+-activated K+ channel in excised membrane patches from bovine aortic smooth muscle. Iberiotoxin acts exclusively at the outer face of the channel and functions with IC₅₀ values of about 250 pM. Iberiotoxin is a partial inhibitor of ¹²⁵I-charybdotoxin binding in bovine aortic sarcolemmal membrane vesicles (Ki of 2₅₀ pM). Iberiotoxin functions as a noncompetitive inhibitor of charybdotoxin binding^[1].
Iberiotoxin treatment affects rat mesenchymal stem cells (rMSCs) migration in the absence of platelet lysate (PL) by inducing a decrease in cell migration suggesting that BK channels regulate rMSCs migration in basal conditions. 10 nM of Iberiotoxin abolishes the PL-induced migration effect on MSCs^[2]. In Vivo: Male Wistar rats (6-7 weeks old) with chronic heart failure (CHF), Iberiotoxin (0.125 nmol/nl, 1.25 nmol/nl and 12.5 nmol/nl) is infused into paraventricular hypothalamic nucleus (PVN) by osmotic minipumps. After perfusion of Iberiotoxin by microinjection of rAAV2-KCNMB4 shRNA virus, right ventricular weight/body weight and lung weight/body weight ratio as well as left ventricular end-diastolic diameter are increased and left ventricular ejection fraction is decreased^[4].