The mechanism of honokiol-induced and magnolol-induced inhibition on muscle contraction and Ca2+ mobilization in rat uterus |
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Authors: | Lu Yu-Cheng Chen Hwei-Hsien Ko Chien-Hsin Lin Yi-Ruu Chan Ming-Huan |
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Institution: | (1) Department of Pharmacy, Buddhist Dalin Tzu Chi General Hospital, Chia Yi, Taiwan;(2) Institute of Pharmacology and Toxicology, Tzu Chi University, No. 701, Section 3, Chung Yang Road, 970 Hualien, Taiwan;(3) Institute of Medical Sciences, Tzu Chi University, Hualien, Taiwan;(4) Department of Chinese Medicine, Buddhist Tzu Chi General Hospital, Hualien, Taiwan |
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Abstract: | The effects of honokiol and magnolol extracted from the Magnolia officinalis on muscular contractile responses and intracellular Ca2+ mobilization were investigated in the non-pregnant rat uterus. Honokiol and magnolol (1–100 mol/l) were observed to inhibit spontaneous and uterotonic agonists (carbachol, PGF2, and oxytocin)-, high K+-, and Ca2+ channel activator (Bay K 8644)-induced uterine contractions in a concentration-dependent manner. The inhibition rate of honokiol on spontaneous contractions appeared to be slower than that of magnolol-induced response. The time periods that were required for honokiol and magnolol, at 100 mol/l, to abolish 50% spontaneous contractions were approximately 6 min. Furthermore, honokiol and magnolol at 10 mol/l also blocked the Ca2+-dependent oscillatory contractions. Consistently, the increases in intracellular Ca2+ concentrations (Ca2+]i) induced by PGF2 and high K+ were suppressed by both honokiol and magnolol at 10 mol/l. After washout of these treatments, the rise in Ca2+]i induced by PGF2 and high K+ was still partially abolished. In conclusion, the inhibitory effects of honokiol and magnolol on uterine contraction may be mediated by blockade of external Ca2+ influx, leading to a decrease in Ca2+]i. Honokiol and magnolol may be considered as putative Ca2+ channel blockers and be of potential value in the treatment of gynecological dysfunctions associated with uterine muscular spasm and dysmenorrhea. |
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Keywords: | Honokiol Magnolol Ca2+ Smooth muscle Rat uterus |
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