Effects and Selectivity of CL 316243, Beta-3-Adrenoceptor Agonist, in Term-Pregnant Rat Myometrium

Dec 23, 2011Gynecologic and obstetric investigation

Selective effects of a beta-3 receptor activator on the uterine muscle of full-term pregnant rats

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Abstract

CL 316243 significantly increased cAMP levels in isolated myometrial strips from term-pregnant rats.

CL 316243 inhibited the amplitude of oxytocin-induced myometrial contractions.
The inhibition by CL 316243 was counteracted by the β(3)-adrenoceptor antagonist SR 59230A.
Metoprolol and ICI 118.551 did not alter the effects of CL 316243 on contractions.
CL 316243 also increased cGMP levels, though the increase was less significant than that of cAMP.
Increased cAMP and cGMP levels are associated with the action of CL 316243 on myometrial contractions.

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BACKGROUND/AIMS: Recent evidence supports a predominant role of β(3)-adrenoceptors at the end of pregnancy in myometrium. This study was designed to characterize the pharmacology of the selective β(3)-adrenoceptor agonist CL 316243 on oxytocin-induced myometrial contractions and the levels of cAMP and cGMP of myometrial strips isolated from term-pregnant rats.

METHODS: Myometrial strips were obtained from term-pregnant Wistar albino rats (n = 10), mounted in organ baths and tested for changes in isometric tension in response to CL 316243 (10(-10)-10(-5) M) on oxytocin-induced myometrial contractions. Effects of CL 316243 on cAMP and cGMP levels in isolated myometrial strips (n = 8) were evaluated by radioimmunoassay kits. We evaluated the effect of increasing concentrations of CL 316243 on myometrial contractions and on contractions of myometrial smooth muscle pretreated with metoprolol, ICI 118.551 and SR 59230A (β(1)-, β(2)-, β(3)-adrenoceptor antagonists, respectively, 10(-6) M).

RESULTS: The inhibition of the amplitude of oxytocin-induced contractions by CL 316243 were antagonized with SR 59230A (10(-6) M), but they were not changed by metoprolol (10(-6) M) or ICI 118.551 (10(-6) M). CL 316243 increased cAMP levels compared to the control group. CL 316243 increased cGMP levels, in the CL 316243 group more than in the control group, but this increase is less significant than cAMP levels.

CONCLUSION: These results demonstrate that the inhibition of rat myometrial contractions with CL 316243 is mediated by β(3)-adrenoceptor subtype and increased cAMP and cGMP levels.

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Effects and Selectivity of CL 316243, Beta-3-Adrenoceptor Agonist, in Term-Pregnant Rat Myometrium

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