|
KMID : 0359319960360010083
|
|
Korean Journal of Veterinary Research
1996 Volume.36 No. 1 p.83 ~ p.91
|
|
|
Mechanism of isoproterenol - induced relaxation of the rat uterine smooth muscle
|
|
|
|
|
Abstract
|
|
|
Activation of K^+ channels induces relaxation of smooth muscles by reducing electrical excitability and cytosolic free Ca^(2+) level. β-adrenergic agonist isoproterenol is known to induce relaxation of the uterine smooth muscle by membrane hyperpolarization and K^+ efflux. Recently it is suggested that the activity of Ca^(2+)-activated K^+ channel was increased by isoproterenol in the uterine myocytes isolated from myometrium of the pregnant rat. However, the type of K^+ channel mediating the relaxant effect of isopreterenol in the tissue level has not yet studied. In this work, we investigated the type of K^+ channels involved in the isoproterenol-induced relaxation of uterine smooth muscle by measuring the integrated insometric tension of the estrogen-treated isolated nonpregnant rat uterus. Contraction of uterine tissue was induced by oxytocin (0.2nM, 2∼3 contractions/min) or high KCl(20∼80mM).
The result are as follows: 1. Isoproterenol(10^(-10)∼10^(-4)M) inhibited oxytocin-induced contraction of isolated rat uterus(EC_(50)=1.17×10^(-10)M). 2. Isoproterenol(10^(-10)∼10^(-4)M) effectively inhibited uterine contraction induced by low KCl(20∼40mM) but little those induced by high KCl(60∼80mM). 3. Relaxant effect of isoproterenol(10^(-10)∼10^(-4)M) on 0.2nM oxytocin-induced contraction was effectively reduced by 4-aminopyridine(3, 10mM) but little by TEA(10∼30mM), Ba^(2+) (1∼30μM) and glibenclamide(100μM).
Our data suggest that the relaxant effect of isoproterenol is mediated by the K^+ channel(s) which can be blocked by 4-aminopyridine.
|
|
|
KEYWORD
|
|
|
|
|
|
FullTexts / Linksout information
|
|
|
|
|
|
Listed journal information
|
|
|