The mechanism of honokiol-induced and magnolol-induced inhibition on muscle contraction and Ca 2+ mobilization in rat uterus

Sep 25, 2003Naunyn-Schmiedeberg's archives of pharmacology

How honokiol and magnolol reduce muscle contractions and calcium movement in rat uterus

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Abstract

Honokiol and magnolol inhibited uterine contractions in non-pregnant rats in a concentration-dependent manner.

Both compounds were effective at concentrations ranging from 1-100 micromol/l.
Magnolol showed a faster inhibition rate on spontaneous contractions compared to honokiol.
At 100 micromol/l, honokiol and magnolol abolished 50% of spontaneous contractions within approximately 6 minutes.
Both substances blocked oscillatory contractions and suppressed increases in intracellular calcium levels induced by specific agonists.
The effects suggest that honokiol and magnolol may act as calcium channel blockers, potentially providing therapeutic benefits for uterine muscular spasms.

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The effects of honokiol and magnolol extracted from the Magnolia officinalis on muscular contractile responses and intracellular Ca(2+) mobilization were investigated in the non-pregnant rat uterus. Honokiol and magnolol (1-100 micromol/l) were observed to inhibit spontaneous and uterotonic agonists (carbachol, PGF(2alpha), and oxytocin)-, high K(+)-, and Ca(2+) 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 micromol/l, to abolish 50% spontaneous contractions were approximately 6 min. Furthermore, honokiol and magnolol at 10 micromol/l also blocked the Ca(2+)-dependent oscillatory contractions. Consistently, the increases in intracellular Ca(2+) concentrations ([Ca(2+)](i)) induced by PGF(2alpha) and high K(+) were suppressed by both honokiol and magnolol at 10 micromol/l. After washout of these treatments, the rise in [Ca(2+)](i) induced by PGF(2alpha) 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 Ca(2+) influx, leading to a decrease in [Ca(2+)](i). Honokiol and magnolol may be considered as putative Ca(2+) channel blockers and be of potential value in the treatment of gynecological dysfunctions associated with uterine muscular spasm and dysmenorrhea.

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The mechanism of honokiol-induced and magnolol-induced inhibition on muscle contraction and Ca 2+ mobilization in rat uterus

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