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Potent inhibition of spontaneous rhythmic contraction by a novel beta 2-adrenoceptor agonist, HSR-81, in pregnant rat uterus.

Abstract：

:We examined the effect of HSR-81 ((-)-(R)-alpha-[(tert-butylamino)methyl]-2-chloro-4-hydroxybenzyl alcohol L-tartrate), a newly developed, potent and selective beta 2-adrenoceptor agonist, as well as ritodrine and isoproterenol, on the spontaneous rhythmic contraction in uteri isolated from late pregnant, middle pregnant and non-pregnant (dioestrous and oestrous) rats. The three agonists inhibited the spontaneous rhythmic contraction at all the stages in a concentration-dependent manner. The pD2 value for HSR-81 was greater in late pregnancy than in dioestrus and oestrus. In the uterine preparations of late pregnancy and dioestrus, ICI-118,551 (1-(7-methylindan-4-yloxy)-3-isopropyl-aminobutan-2-ol , a selective beta 2-adrenoceptor antagonist) and atenolol (a selective beta 1-adrenoceptor antagonist) produced a parallel rightward shift of the concentration-response curves for HSR-81. The pKB values for ICI-118,551 and atenolol suggest that the inhibitory effect of HSR-81 was mediated through beta 2-adrenoceptors in the two stages. In the membranes prepared from rat uteri in late pregnancy and dioestrus, the equilibrium dissociation constant for [125I]iodocyanopindolol binding was not significantly different between the two stages. The three beta-adrenoceptor agonists and the two antagonists competed for the specific [125I]iodocyanopindolol binding and the pKi values were not significantly different between the two stages. However, the maximum number of binding sites was significantly greater in late pregnancy than in dioestrus. The configuration of the competition curves and the pKi values for the two antagonists confirmed the fact that these membranes contain predominantly beta 2-adrenoceptor subtype. These results indicate that the potent inhibition of the spontaneous rhythmic contraction by HSR-81 in the pregnant uterus may be due to the increased number of beta 2-adrenoceptors.

journal_name

Eur J Pharmacol

journal_title

European journal of pharmacology

authors

Ohashi T,Hashimoto S,Morikawa K,Kato H,Ito Y,Asano M,Azuma H

doi

10.1016/0014-2999(96)00277-4

subject

Has Abstract

pub_date

1996-07-04 00:00:00

pages

315-22

issue

eissn

0014-2999

issn

1879-0712

pii

0014299996002774

journal_volume

307

pub_type

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Potent inhibition of spontaneous rhythmic contraction by a novel beta 2-adrenoceptor agonist, HSR-81, in pregnant rat uterus.