title: EDRF-release and Ca+(+)-channel blockade by magnolol, an antiplatelet agent isolated from Chinese herb Magnolia officinalis, in rat thoracic aorta.
abstract: Magnolol is an antiplatelet agent isolated from Chinese herb Magnolia officinalis. It inhibited norepinephrine (NE, 3 microM)-induced phasic and tonic contractions in rat thoracic aorta. At the plateau of the NE-induced tonic contraction, addition of magnolol caused two phases (fast and slow) of relaxation. These two relaxations were concentration-dependent (10-100 micrograms/ml), and were not inhibited by indomethacin (20 microM). The fast relaxation was completely antagonized by hemoglobin (10 microM) and methylene blue (50 microM), and disappeared in de-endothelialized aorta while the slow relaxation was not affected by the above treatments. Magnolol also inhibited high potassium (60 mM)-induced, calcium-dependent (0.03 to 3 mM) contraction of rat aorta in a concentration-dependent manner. 45Ca(+)+ influx induced by high potassium or NE was markedly inhibited by magnolol. Cyclic GMP, but not PGI2, was increased by magnolol in intact, but not in de-endothelialized aorta. It is concluded that magnolol relaxed vascular smooth muscle by releasing endothelium-derived relaxing factor (EDRF) and by inhibiting calcium influx through voltage-gated calcium channels.
authors.affiliation: Pharmacological Institute, College of Medicine, National Taiwan University, Taipei.
authors.forename: C M
authors.initials: CM
authors.lastname: Teng
authors.forename: S M
authors.initials: SM
authors.lastname: Yu
authors.forename: C C
authors.initials: CC
authors.lastname: Chen
authors.forename: Y L
authors.initials: YL
authors.lastname: Huang
authors.forename: T F
authors.initials: TF
authors.lastname: Huang
mesh_terms: D000818:Animals; D001011:Aorta / Q000187:drug effects; D001713:Biphenyl Compounds / Q000302:isolation & purification / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects*; D006152:Cyclic GMP / Q000378:metabolism; D004365:Drugs, Chinese Herbal / Q000302:isolation & purification / Q000494:pharmacology*; D004730:Endothelium, Vascular / Q000187:drug effects; D011464:Epoprostenol / Q000378:metabolism; D005260:Female; D006454:Hemoglobins / Q000494:pharmacology; D066298:In Vitro Techniques; D017705:Lignans; D008297:Male; D008751:Methylene Blue / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D010975:Platelet Aggregation Inhibitors / Q000302:isolation & purification / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D014661:Vasoconstriction / Q000187:drug effects*
chemical_list: D001713:Biphenyl Compounds; D015220:Calcium Channels; D004365:Drugs, Chinese Herbal; D006454:Hemoglobins; D017705:Lignans; D010975:Platelet Aggregation Inhibitors; C005498:magnolol; D009569:Nitric Oxide; D011464:Epoprostenol; D006152:Cyclic GMP; D002118:Calcium; D008751:Methylene Blue; D009638:Norepinephrine