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In vitro study of the tocolytic effect of oroxylin A from Scutellaria baicalensis root.

Shih HC, Hsu CS, Yang LL - J. Biomed. Sci. (2009)

Bottom Line: 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Pharmacy, College of Pharmacy, Taipei Medical University, 250 Wu-Hsing Street, Taipei 110, Taiwan. d001089008@tmu.edu.tw

ABSTRACT
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.

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Effects of the potassium channel inhibitor, 4-aminopyridine (4-AP), on oroxylin A-induced uterine relaxation. Vertical bars represent the SEM (n = 4). *p < 0.05, **p < 0.01.
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Figure 6: Effects of the potassium channel inhibitor, 4-aminopyridine (4-AP), on oroxylin A-induced uterine relaxation. Vertical bars represent the SEM (n = 4). *p < 0.05, **p < 0.01.

Mentions: Preincubation of uterine rings from rats with the nonspecific potassium channel inhibitor, TEA (1 and 10 mM), shifted the concentration-response curve of oroxylin A and attenuated the relaxation activity induced by oroxylin A (Fig. 5). Concentrations causing 50% of the inhibition concentration were 52.73 μM and 76.43 μM in the presence of 1 and 10 mM TEA, respectively. The result indicates that relaxation of oroxylin A is inhibited by TEA. In the same part of the experiment, pretreatment of the uterine muscle with other potassium channel inhibitors, including 4-AP and glipizide, showed significant inhibition of oroxylin A-induced relaxation with IC50 values of 67.16 μM and 27.53 μM, respectively (Figs. 6, 7). Upon comparison with the results of these potassium channel antagonists, TEA appeared more effective than glipizide in attenuating of oroxylin A-induced uterine relaxation. Therefore, activation of potassium channels in the myometrium including Ca2+-dependent or ATP-dependent potassium channels is involved in oroxylin A-induced uterine relaxation.


In vitro study of the tocolytic effect of oroxylin A from Scutellaria baicalensis root.

Shih HC, Hsu CS, Yang LL - J. Biomed. Sci. (2009)

Effects of the potassium channel inhibitor, 4-aminopyridine (4-AP), on oroxylin A-induced uterine relaxation. Vertical bars represent the SEM (n = 4). *p < 0.05, **p < 0.01.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2656494&req=5

Figure 6: Effects of the potassium channel inhibitor, 4-aminopyridine (4-AP), on oroxylin A-induced uterine relaxation. Vertical bars represent the SEM (n = 4). *p < 0.05, **p < 0.01.
Mentions: Preincubation of uterine rings from rats with the nonspecific potassium channel inhibitor, TEA (1 and 10 mM), shifted the concentration-response curve of oroxylin A and attenuated the relaxation activity induced by oroxylin A (Fig. 5). Concentrations causing 50% of the inhibition concentration were 52.73 μM and 76.43 μM in the presence of 1 and 10 mM TEA, respectively. The result indicates that relaxation of oroxylin A is inhibited by TEA. In the same part of the experiment, pretreatment of the uterine muscle with other potassium channel inhibitors, including 4-AP and glipizide, showed significant inhibition of oroxylin A-induced relaxation with IC50 values of 67.16 μM and 27.53 μM, respectively (Figs. 6, 7). Upon comparison with the results of these potassium channel antagonists, TEA appeared more effective than glipizide in attenuating of oroxylin A-induced uterine relaxation. Therefore, activation of potassium channels in the myometrium including Ca2+-dependent or ATP-dependent potassium channels is involved in oroxylin A-induced uterine relaxation.

Bottom Line: 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Pharmacy, College of Pharmacy, Taipei Medical University, 250 Wu-Hsing Street, Taipei 110, Taiwan. d001089008@tmu.edu.tw

ABSTRACT
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.

Show MeSH
Related in: MedlinePlus