Regulation of uterine GABA_A receptor subunit expression throughout pregnancy

[目的]GABA_A受体的一个新的亚基，命名为它，仅在子宫中丰富。由于别孕酮通过GABAA受体发挥作用，减少子宫收缩，α亚基可能改变GABAA受体对别孕酮的敏感性，从而调节分娩。本研究的目的是检测不同胎龄大鼠子宫组织中GABA_A受体亚基的表达，特别是n亚基的表达，并探讨其与生理特性的相关性。[方法]取定时妊娠大鼠(13.5~21.5天)、未孕育种者和产后第1天大鼠的子宫组织，获取质膜和RNA。用核糖核酸酶保护法检测GABAA受体π亚单位和3HSDmRNA在整个妊娠过程中的表达。我们还通过…检测了大鼠子宫中其他GABAA受体亚单位的表达半定量聚合酶链式反应检测妊娠情况。[结果]分娩开始时GABAAπ亚单位基因表达下降，产后第1天3αHSDmRNA表达下降。半定量聚合酶链式反应显示GABAAα1亚基表达增加，α2和α亚基表达降低，α3亚基仅在产后第1天出现。非妊娠子宫GABA_A受体与~3H-蝇草酚具有高亲和力结合部位(Kd=1.79 nM，Bmax=4.9pmole/mg蛋白)和低亲和力结合部位(Kd=52.6 nM，Bmax=12.1pmole/mg蛋白)。结合实验结果表明，子宫内GABAA受体在19.5天时对别孕酮最敏感，分娩时最不敏感。[结论]不同孕期子宫内GABAA受体的亚基组合不同。亚基的每一种组合的功能仍不清楚。但妊娠期间GABAA受体亚单位表达的不同可能改变了GABAA受体对别孕酮的敏感性，对分娩有调节作用。较少

[OBJECTIVE] A new subunit of GABA_A receptor, named it, is abundant only in the uterus. Since allopregnanolone works through the GABA_A receptor and reduce uterine contraction, α subunit might change the sensitivity of GABA_A receptor to allopregnanolone and modulate the parturition. The purpose of this study was to determine the expressions of GABA_A receptor subunits in the uteri from various gestational ages, especially for the n subunit, and examine the correlation between the combination of the subunits and physiological properties.[METHODS] Uterine tissues from the timed pregnant rats (13.5 - 21.5 gestational days), non-pregnant proven breeders and postpartum day-1 rats were used to obtain plasma membranes and RNAs. Following RT-PCR and subcloning, RNase protection assay was performed to determine the mRNA expressions of GABA_A receptor π subunit and 3 HSD throughout the pregnancy. We also examined the expressions of the other GABA_A receptor subunits in the rat uteri throughout … More the pregnancy by semi-quantitative PCR. Then we performed ^3H-muscimol binding assay to the GABA_A receptor on the plasma membranes in various gestational uteri and examined the difference of the effect of allopregnanolone on the binding.[RESULTS] The expression of GABA_A π subunit mRNA was decreased at onset of labor, and 3αHSD mRNA were decreased on postpartum day-1. Semi-quantitative PCR study showed that GABA_Aα1 subunit expression was increased, while α2 and α subunits expressions were decreased during the pregnancy, and α3 subunit only appeared on postpartum day-1. GABA_A receptor in non-pregnant uterus appeared to have the high affinity binding site (Kd=1.79nM, Bmax=4.9pmole/mg protein) and the low affinity binding site (Kd=52.6nM, Bmax=12.1pmole/ mg protein) to ^3H-muscimol. And the results of the binding assay showed that the GABA_A receptor in uteri was most sensitive to allopregnanolone on 19.5 days gestation and was least sensitive in labor.[CONCLUSION] We detected that the subunits combinations of the GABA_A receptor are different in the uteri from various gestational days. The function of the each combination of the subunits is still unclear. However it was suggested that the difference of GABA_A receptor subunit expression during pregnancy may change the sensitivity of GABA_A receptor to allopregnanolone and have a regulating effect on the parturition. Less