178 DISTINCT EXPRESSION AND REGULATION OF ECTONUCLEOTIDE PYROPHOSPHATASE/PHOSPHODIESTRASE 2 AND ITS POTENTIAL ROLE(S) IN THE UTERUS OF RATS DURING ESTROUS CYCLE

Abstract

Ectonucleotide pyrophosphatase/phosphodiestrase 2 (ENPP2) is a recently discovered phospholipase D that transforms lysophosphatidylycholine into lysophospatidic acid. Previously, multiple analyses have been carried out to identify oestrogen response genes, such as ENPP2, in the hypothalamus. However, little is known about the role(s) of the ENPP2 gene in the uterus during the oestrous cycle and the mechanism(s) of its regulation. In this study, the ENPP2 gene was investigated using RT-PCR, Western blot, and immunohistochemistry analyses in the uterine of rats. Quantitative PCR analysis demonstrated that the levels of uterine ENPP2 mRNA decreased at oestrus compared with those at proestrus and diestrus. To investigate whether ENPP2 expression is affected by sex steroid hormone in the uterus of rats, we treated rats with 17β-oestradiol (E₂), progesterone (P₄), or E₂ plus P₄ from postnatal Day 14 to 16 in an immature rat model. Interestingly, ENPP2 mRNA and protein level expression was down-regulated by E₂ in the uterus at oestrus, but not in the proestrus and diestrus, suggesting that the ENPP2 gene may be involved in uterine function during the oestrous cycle. Using immunohistochemistry with a specific antibody, we demonstrated the expression of ENPP2 protein localization in the uterus of rats during the oestrous cycle. In particular, ENPP2 was mainly located in the stromal cells in the uterine endometrium at the proestrus and oestrus cycles. The diestrous stage showed greater expression, and ENPP2 was mainly expressed in decidual cells. In conclusion, these results suggest that uterine ENPP2 induction is caused by steroid hormones during the oestrous cycle in rats, and this gene may be involved in reproductive function during a critical developmental stage of female rats.