子宫液体微环境酸碱稳态对精子获能、受精及胚胎早期发育等过程有重要影响。宫内液体含有高浓度的碳酸氢根，是精子获能必需的因子。子宫内碳酸氢根浓度随动情周期而周期性地变化。目前研究已阐明子宫内膜上皮细胞中存在碳酸氢根分泌机制，调控子宫微环境的酸碱稳态。在前期研究中我们发现Na+/HCO3–共转运体NBCn1特异表达在子宫内膜上皮细胞顶膜，提示NBCn1在此介导碳酸氢根吸收。据此，我们提出研究假设：子宫内膜上皮细胞存在一种新的碳酸氢根吸收机制，机体通过分泌机制与吸收机制的动态平衡维持宫内微环境的酸碱稳态。在此，我们将利用模式动物，通过离体组织灌流技术研究NBCn1在子宫内膜上皮碳酸氢根转运机制中的作用，研究NBCn1的表达及活性变化与动情周期的关系，研究生殖激素对NBCn1表达的调控作用及机制。该研究对了解雌性生殖的机理将有重要科学意义，对生殖健康、计划生育、不孕不育治疗亦有重要的实际应用价值。

Acid-base regulation plays a critical role in mammalian reproduction. Specifically, the luminal fluid in uterine cavity contains very high concentration of HCO3–, a component that is essential for the function of sperm, such capacitation, motility, and fertilization. Moreover, the HCO3– concentration in uterine fluid milieu periodically changes during the estrous cycle. It has been well established that the endometrial epithelia contain the machinery for secreting HCO3– from the cells into uterine cavity to achieve the high concentration of HCO3– in uterine fluid milieu..Our preliminary study showed that the Na+/HCO3– cotransporter NBCn1 is abundantly expressed on the apical membrane of endometrial epithelial cells. Based upon our preliminary data, we propose that the endometrial epithelia contain a novel mechanism, of which the apical NBCn1 is a key component, for reabsorbing HCO3– from the uterine fluid into the epithelial cells. We hypothesize that the acid-base homeostasis in the uterine fluid milieu is achieved by the fine balance between the activity of the well-known HCO3–-secreting machinery and that of our novel HCO3–-reabsorbing machinery..Based upon our hypothesis, we developed the present project to investigate the physiological role of NBCn1 in acid-base regulation in the endometrial epithelial cells by using rodent as the model animal. Firstly, we will examine the expression of NBCn1-dependent HCO3–-reabsorbing activity in the apical membrane of the endometrial epithelia by using microperfusion of isolated uterus..Secondly, we will examine, as a function of the estrous cycle, the changes in the expression profile, the cellular localization, as well as the HCO3– transport activity of NBCn1 in endomentrial epithelia. As a component of the HCO3–-reabsorbing machinery, we expect that the surface-protein abundance and transport activity of NBCn1 in the endometrial apical membrane would be upregulated during the metestrus stage, and would be down-regulated during the estrus stage..Finally, we will examine the mechanism underlying the cyclic regulation of the expression and activity of NBCn1 in the endometrial epithelial cells. Particularly, we will examine the role of estrogen and progesterone in regulating the expression of Slc4a7 gene encoding NBCn1 in the endometrial epithelia..We believe that our study is important for understanding the molecular mechanism underlying female reproduction. It is also clinically important for, for example, birth control and the treatment of female infertility.