Catharanthine showed muscarinic antagonism at 10 μM and fully inhibited nicotinic receptor mediated diaphragm contractions with an IC50 of 59.6 μM. As a precursor of the anti-tumor drugs vinblastine and vincristine, it also works as an inhibitor of tubulin self-assembly into microtubules.
Catharanthine is a constituent of anticancer vinca alkaloids. Catharanthine evoked concentration-dependent decreases (I(max) >98%) in endothelium-independent tonic responses of aortic rings to phenylephrine (PE) and KCl (IC50 = 28 µM for PE and IC50 = 34 µM for KCl) and of third-order branches of the small mesenteric artery (MA) (IC50 = 3 µM for PE and IC50 = 6 µM for KCl). Catharanthine also increased the inner vessel wall diameter (IC50 = 10 µM) and reduced intracellular free Ca2+ levels (IC50 = 16 µM) in PE-constricted MAs. Patch-clamp studies demonstrated that catharanthine inhibited voltage-operated L-type Ca2+ channel (VOCC) currents in cardiomyocytes and VSMCs (IC50 = 220 µM and IC50 = 8 µM, respectively) of MA[3].
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