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

Dec 15, 2011Acta pharmaceutica Hungarica

Development of sugar-sensitive channel regulators in the muscle layer of pregnant rat uterus

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Abstract

SUR1 levels in the pregnant rat myometrium increased significantly, peaking on day 6 of pregnancy.

SUR1 and SUR2 are the sulphonylurea-binding regulatory subunits of K(ATP) channels.
SUR1 levels were markedly elevated in early pregnancy but decreased significantly in later stages.
SUR2 levels remained unchanged throughout the pregnancy.
Both SUR-non-selective diazoxide and SUR2-selective pinacidil inhibited oxytocin-induced contractions.
Glibenclamide blocked relaxations induced by both pinacidil and diazoxide.
SURs are associated with the pharmacological response of K(ATP) channel openers in the pregnant myometrium.

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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. RT-PCR and Western blot analysis were performed to detect the presence of SUR1 and SUR2. The SUR1 levels were markedly increased in the early stages of pregnancy. The highest level was detected on day 6 of pregnancy, while in the late stages the levels of SUR1 were significantly decreased. The SUR2 level remained unchanged throughout pregnancy. The SUR-non-selective diazoxide and the SUR2-selective pinacidil inhibited oxytocin-induced contractions. Glibenclamide, a K(ATP) channel blocker, antagonized both pinacidil and diazoxide-induced relaxations. It was established that SURs are responsible for pharmacological reactivity of K(ATP) channel openers. We conclude that, both SURs are involved in the K(ATP) channel in the pregnant rat myometrium. It may further be concluded that "pinacidil-like" K(ATP) channel openers may be of therapeutic relevance as tocolytic agents in the future.

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

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