The effects of female sexual hormones on the expression and function of α1A- and α1D-adrenoceptor subtypes in the late-pregnant rat myometrium

The aim of the study was to investigate the roles of alpha(1)-adrenoceptor subtypes in the last-day pregnant rat uterus in vitro by the administration of subtype-specific antagonists (the alpha(1A)-adrenoceptor antagonist WB 4101 and the alpha(1D)-adrenoceptor antagonist BMY 7378) after 17 beta-estradiol or progesterone pretreatment. In isolated organ bath studies, contractions were elicited with (-)-noradrenaline (10(-5)-10(-5) M) in the presence of propranolol (10(-5) M) and yohimbine (10(-6) M) in order to avoid beta-, and alpha(2)-adrenergic action. The myometrial expressions of the oci-adrenoceptor subtypes were determined by means of the real time reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting techniques. The activated G protein levels were investigated through radiolabelled GTP binding assays. Both 17 beta-estradiol and progesterone pretreatment changed the myometrial contracting effect of (-)-noradrenaline. In the presence of WB 4101, progesterone pretreatment decreased the (-)-noradrenaline-induced myometrial contraction. In the presence of BMY 7378, both the 17 beta-estradiol and the progesterone pretreatment reduced the effect of (-)-noradrenaline. The mRNA and protein expressions of the alpha(1A)-adrenoceptors were decreased after 17 beta-estradiol pretreatment. (-)-Noradrenaline increased the [S-35]GTP gamma S binding of the alpha(1)-adrenoceptors, which was most markedly elevated by progesterone. Pertussis toxin inhibited the [S-55]GTP gamma S binding-stimulating effect of (-)-noradrenaline, indicating the role of G(i) proteins in the signal mechanisms. 17 beta-estradiol pretreatment blocks the expression of the alpha(1A)-adrenoceptors, whereas it does not influence the expression of the alpha(1p)-adrenoceptors. Progesterone pretreatment does not have any effect on the myometrial mRNA and protein expressions of the alpha(1)-adrenoceptors, but it alters the G protein coupling of these receptors, promoting a G(i)-dependent pathway. (C) 2015 Elsevier B.V. All rights reserved.