The endometrium is hostile to embryo implantation except during the window of receptivity. A change in endometrial gene expression is required for the development of receptivity. The uterine calcium balance is crucial for physiological functioning, including smooth muscle contraction and embryo implantation. The location of cytoplasmic calcium-related proteins (CRP) include the calcium transporters 1 (CaT1), calbindin-D9k/-D28k (CaBP- 9k/28k), plasma membrane Ca2+-ATPase 1b (PMCA1b), sodium/calcium exchangers (NCX1), and potassium-dependent Na+/Ca2+ exchanger (NCKX3). The expressions of these CRP and their potential roles in the uterus of human during the menstrual cycle remain to be clarified. Thus, in this current study, the expression patterns of CRP were examined for their roles in the human uterus during the menstrual cycle. Human endometrial tissues were collected by curettage from women undergoing hysteroscopy for investigation of tubal patency or tubal ligation. Approval was given by the Human Ethics Committee at SCH Medical Center, Bucheon, and signed consent was obtained in every case. Human uterus (total n = 51) were divided into 3 groups: menstrual, proliferative, and secretory phase. Reverse-transcription PCR and Western blot analysis were applied to measure the level of CRP mRNA and protein, respectively. During the menstrual cycle of human, the expression levels of CaT1 mRNA and protein were increased 5-fold at proliferative phase (Days 6 to 13) compared with secretory phase in the endometrium of uterus. The expression of CaBP-28k mRNA and protein was less 2-fold during the proliferative phase (Days 6 to 13) than during the secretory phase (Days 16 to 28). However, the expressions of NCX1, NCKX3, and PMCA1b mRNA and protein were not altered during cycle, whereas the expression of CaBP-9k was not observed in the uterus of human. In addition, spatial expression of CRP was detected by immunohistochemistry Uterine CRP was abundantly localized in the cytoplasm of the luminal and glandular epithelial cells during menstrual cycle. Taken together, these results indicate that uterine CRP is abundantly expressed in the uterus, suggesting that uterine expression of CRP might be involved in reproductive function during the menstrual cycle in human.
Concentrations of steroid hormones, and of prolactin, in washings of the human uterus during the menstrual cycle