191 TRANSIENT RECEPTOR POTENTIAL SUPERFAMILY OF ION CHANNELS, TRPV6, IS CONSTITUTIVELY EXPRESSED AND REGULATED BY ESTROGEN IN THE HUMAN UTERUS DURING THE MENSTRUAL CYCLE

Abstract

Two highly selective calcium channels at the apical sides of cells, members of the transient receptor potential (TRP) superfamily of ion channels (TRPV6 and TRPV5), are the main calcium ion entry channels. Previously, the location of TRPV6 has been described in the intestine in several species, including humans. It is located in the apical brush-border membrane of the intestinal enterocyte, where it regulates calcium entry into the cell. It is most abundant in the proximal small intestine (duodenum and jejunum), where calbindin and the calcium-pumping ATPase are also found. The TRPV6 calcium transporter is also found in the human placenta, pancreas, and prostate gland in some species. However, TRPV6 expression and its potential roles remain to be clarified in the endometrium of humans during the menstrual cycle. In this study, we used a human endometrial model to examine the expression of TRPV6 and its potential roles in the human menstrual cycle. A significant increase (1.5-fold) in the TRPV6 transcript and protein was observed in the human uterus at the proliferation phase compared with other phases. In addition, the spatial localization of TRPV6 in the human uterus was determined by immunohistochemistry. Uterine TRPV6 was abundantly localised in the cytoplasm of the endometrial and glandular epithelial cells in the menstrual phases. Overall, these results demonstrate that TRPV6 is abundantly expressed in human uterine tissue, suggesting that this protein may be involved in reproductive functions during the menstrual cycle in humans.