In vitro study of the tocolytic effect of oroxylin A from Scutellariabaicalensis root

摘要

Scutellariae Radix is one of the well-known tocolytic Chinese herbs. Oroxylin A is isolated fromthe root of Scutellaria baicalensis. The main syndrome of preterm birth is caused by uteruscontractions from excitatory factors. Administration of tocolytic agents is a strategy to prevent theoccurrence of preterm births. The aim of this study was to investigate the effects of oroxylin A oncontractions of uterine strips isolated from non-pregnant female Wistar rats (250~350 g).Contractions of the uterus were induced with acetylcholine (Ach) (1muM), PGF2alpha (0.1muM),oxytocin (10-3 mu/ml), KCl (56.3 mM), tetraethylammonium (TEA; 1 and 10 mM), 4-aminopyridine(4-AP; 5 mM), glipizide (30muM), a nitric oxide synthase (NOS) inhibitor (LNNA; 10-3M), a beta?-receptor blocker (propranolol; 10muM), and a cyclooxygenase inhibitor (indomethacin; 60muM). Theinhibitory effects of the amplitude and frequency of spontaneous contractions by oroxylin A wereantagonized with Ach (IC50 22.85muM), PGF2? (IC5027.28muM), oxytocin (IC50 12.34muM), TEA; 1 and10 mM (IC_50 52.73 and 76.43muM), 4-AP (IC50 67.16muM), and glipizide (IC5027.53muM), but oroxylinA was not influenced by Ca2+-free medium, LNNA, propranolol, or indomethacin. Otherwise,oroxylin A-mediated relaxation of the rat uterus might occur through opening of uterine calciumdependentpotassium channels or adenosine triphosphate potassium channel activation. Thissuggests that oroxylin A is the tocolytic principle constituent of Scutellariae Radix, and oroxylin Amay provide a lead compound for new tocolytic drug development in the future.