In vitro study of the tocolytic effect of oroxylin A from Scutellaria baicalensis root.
Scutellariae Radix is one of the well-known tocolytic Chinese herbs. Oroxylin A is isolated from the root of Scutellaria baicalensis. The main syndrome of preterm birth is caused by uterus contractions from excitatory factors. Administration of tocolytic agents is a strategy to prevent the occurrence of preterm births. The aim of this study was to investigate the effects of oroxylin A on contractions of uterine strips isolated from non-pregnant female Wistar rats (250-350 g). Contractions of the uterus were induced with acetylcholine (Ach) (1 microM), PGF2alpha (0.1 microM), oxytocin (10-3 U/ml), KCl (56.3 mM), tetraethylammonium (TEA; 1 and 10 mM), 4-aminopyridine (4-AP; 5 mM), glipizide (30 microM), a nitric oxide synthase (NOS) inhibitor (LNNA; 10-3M), a beta-receptor blocker (propranolol; 10 microM), and a cyclooxygenase inhibitor (indomethacin; 60 microM). The inhibitory effects of the amplitude and frequency of spontaneous contractions by oroxylin A were antagonized with Ach (IC50 22.85 microM), PGF2alpha (IC5027.28 microM), oxytocin (IC50 12.34 microM), TEA; 1 and 10 mM (IC50 52.73 and 76.43 microM), 4-AP (IC50 67.16 microM), and glipizide (IC5027.53 microM), but oroxylin A 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 calcium-dependent potassium channels or adenosine triphosphate potassium channel activation. This suggests that oroxylin A is the tocolytic principle constituent of Scutellariae Radix, and oroxylin A may provide a lead compound for new tocolytic drug development in the future.
Shih
Huey-Chuan
HC
School of Pharmacy, College of Pharmacy, Taipei Medical University, 250 Wu-Hsing Street, Taipei 110, Taiwan. d001089008@tmu.edu.tw
Hsu
Chun-Sen
CS
Yang
Ling-Ling
LL
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D015237:Dinoprost / Q000494:pharmacology; D005260:Female; D005419:Flavonoids / Q000494:pharmacology*; D008516:Medicine, Chinese Traditional; D015394:Molecular Structure; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology; D010121:Oxytocin / Q000494:pharmacology; D010936:Plant Extracts / Q000494:pharmacology*; D018517:Plant Roots / Q000737:chemistry*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism; D011247:Pregnancy; D051381:Rats; D017208:Rats, Wistar; D031364:Scutellaria baicalensis / Q000033:anatomy & histology / Q000737:chemistry; D015149:Tocolytic Agents / Q000494:pharmacology*; D014590:Uterine Contraction / Q000187:drug effects*; D014599:Uterus / Q000033:anatomy & histology / Q000187:drug effects
D016861:Cyclooxygenase Inhibitors; D005419:Flavonoids; D010936:Plant Extracts; D026902:Potassium Channel Blockers; D015221:Potassium Channels; C499814:Scutellaria baicalensis extract; D015149:Tocolytic Agents; D010121:Oxytocin; C080669:5,7-dihydroxy-6-methoxy-2-phenylchromen-4-one; D015237:Dinoprost; D000109:Acetylcholine