ATP-sensitive potassium channels modulate in vitro tocolytic effects of β₂-adrenergic receptor agonists on uterine muscle rings in rats in early but not in late pregnancy.

Aim: To investigate whether ATP-sensitive potassium (K(ATP)) channels modulate the tocolytic effect of β2-adrenergic receptor (β2-AR) agonists (ritodrine and salmeterol) in early-pregnant (day 6) and late-pregnant (day 22) rat uterus in vitro, in order to examine the relation between the K(ATP) channel sulphonylurea-binding regulatory subunit (SUR) expression and pharmacological reactivity of β2-AR agonists.

Methods: The tocolytic effects of ritodrine and salmeterol (10(-10)-10(-5) M) on spontaneous rhythmic contractions were investigated cumulatively, alone, or in the presence of the K(ATP) channel blocker glibenclamide (10(-6) M) and the K(ATP) channel opener pinacidil (10(-9)-10(-7) M) after 5-min preincubation.

Results: β2-AR agonist induced myometrial relaxation was inhibited by glibenclamide and enhanced by pinacidil on day 6, when SUR1 expression levels were high.

Sympathomimetic activity of a Hoodia gordonii product: a possible mechanism of cardiovascular side effects.

Hoodia gordonii, a popular appetite suppressant, is widely used as an ingredient in many food supplements despite the fact that supporting scientific evidence is scarce. Recently alarming side effects of H. gordonii products (increased blood pressure and elevated pulse rate) have been reported.

Increase of the uterus-relaxant effect of nifedipine by the Abcg2 efflux protein inhibitor KO134 in the rat in vivo.

Background/aim: High Abcg2 (ATP-Binding Cassette Transporter Subfamily G, Member-2) levels have been found in reproductive tissues, such as the placenta and uterus. The substrate specificity of Abcg2 is very wide, including uterus-relaxant agents (e.g.

[Ontogeny of sulphonylurea-binding regulatory subunits of K(ATP) channels in the pregnant rat myometrium].

K(ATP) channels are composed of sulphonylurea receptors (SURs) and potassium inward rectifiers (Kir(6.x)) that assemble to form a large octameric channel. This study was designed to examine the expression and role of sulphonylurea-binding regulatory subunits 1 [SUR1 (ABCC8)] and 2 [SUR2 (ABCC9)] of the K(ATP) channels in the pregnant rat myometrium with particular regard to the contractility.