203 PLASMA MEMBRANE Ca²⁺-PUMPING ATPase 1 IS ABUNDANTLY EXPRESSED AND DISTINCTLY REGULATED BY ESTROGEN IN HUMAN ENDOMETRIUM DURING THE MENSTRUAL CYCLE

Abstract

Plasma membrane Ca²⁺-pumping ATPases (PMCA) play a critical role in maintaining cellular Ca²⁺ homeostasis. The PMCA mRNA are encoded on 4 genes, designated PMCA1 to PMCA4. In a previous study, we found that both PMCA1 and PMCA4 are expressed at similar levels in astrocytes and in neurons. Although PMCA1b is expressed in the uterus of rats during the oestrous cycle, the expression of PMCA1 and its potential roles has not been elucidated during the menstrual cycle in the human endometrium. Thus, in the current study, the expression pattern of PMCA1 was examined to predict its roles in the human endometrium during the menstrual cycle. Human uterine tissues (total n = 40) were separated into 3 groups according to menstrual cycle phase: menstrual phase, proliferative phase (early, mid, late), and secretory phase (early, mid, late). Using real-time PCR and Western blot analysis, uterine expression of PMCA1 mRNA and protein increased to 1.5-fold in the early-, mid- and late-proliferative phases in the endometrium of the human uterus, compared with other menstrual phases. In addition, uterine PMCA1 was abundantly localised in the cytoplasm of the luminal and glandular epithelial cells in the menstrual phases, indicating that this protein may participate in the uterine Ca balance of the human endometrium during the menstrual cycle. Taken together, these results suggest that a high level of uterine PMCA1 expression may be involved in reproductive functions during the menstrual cycle of humans.