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The mode of vasoinhibitory action of a pyridazione derivative (MCI-154), a new cardiotonic agent, on contractile responses induced by alpha-adrenoceptor agonists and 45Ca influx in isolated vascular smooth muscles.

Abstract：

:The vasoinhibitory effects of MCI-154 (MCI), a new pyridazione derivative, on contractile responses to alpha 1- and alpha 2-adrenoceptor agonists were examined in isolated rabbit aorta. MCI (10(-8)-10(-5) M) inhibited the maximum contractile responses to clonidine and BHT-920 (BHT) in a concentration-dependent manner, but only inhibited responses to lower concentrations of methoxamine. In aortas pretreated with phenoxybenzamine however, MCI (10(-5) M) readily inhibited responses to methoxamine. MCI (10(-5) M) had no significant effect on responses to potassium or added Ca2+ in a Ca2+ free, K+-depolarizing medium. In aortas incubated in a Ca2+-free medium with EGTA, the addition of methoxamine (10(-5) M), clonidine (10(-5) M) or BHT (3 X 10(-4) M) induced a phasic contraction. The inhibitory effect of MCI (10(-9)-10(-5) M) on these phasic responses was much greater for clonidine or BHT than for methoxamine. In rabbit iliac artery caffeine (10 mM) induced a rapid phasic contraction in a Ca2+-free medium, which was inhibited by MCI (10(-7)-10(-5) M) in a concentration-dependent manner. In aortas incubated in a Ca2+-free medium with low EGTA and nifedipine (10(-6) M) in the presence of alpha-adrenoceptor agonists (methoxamine, clonidine or BHT), the addition of Ca2+ (2 mM) induced a tonic contraction. MCI (10(-8)-10(-5) M) inhibited these Ca2+-dependent, agonists-mediated responses in a concentration-dependent manner. MCI had no effect on unstimulated La3+ resistant Ca2+ binding or methoxamine-induced Ca2+ influx.(ABSTRACT TRUNCATED AT 250 WORDS)

journal_name

Eur J Pharmacol

journal_title

European journal of pharmacology

authors

Shibata S,Satake N,Hester RK,Kurahashi K,Ito M

doi

10.1016/0014-2999(88)90222-1

subject

Has Abstract

pub_date

1988-01-12 00:00:00

pages

113-21

issue

eissn

0014-2999

issn

1879-0712

pii

0014-2999(88)90222-1

journal_volume

145

pub_type

杂志文章

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The mode of vasoinhibitory action of a pyridazione derivative (MCI-154), a new cardiotonic agent, on contractile responses induced by alpha-adrenoceptor agonists and 45Ca influx in isolated vascular smooth muscles.