Lysophosphatidic acid (LPA), a simple phospholipid-derived mediator implicated in diverse biological actions, acts through the specific G-protein coupled receptors, LPA receptor (LPAR) 1～5. Our previous study showed that LPAR3 is expressed in the uterine endometrium in a cell type- and stage-specific manner and LPA via LPAR3 increases PTGS2 expression in the uterine endometrium during the period of implantation. Although LPAR3 is considered to be predominant LPA receptor in the uterine endometrium, other LPA receptors might play a role to mediate LPA functions in the uterine endometrium during pregnancy. Among LPARs, we investigated expression of LPAR1 during the estrous cycle and pregnancy in this study. Uterine endometrial tissue samples were collected from day (D) 12 and D15 of the estrous cycle and from D12, D15, D30, D60, D90 and D114 of pregnancy. Northern blot analysis determined that LPAR1 mRNA was constitutively expressed in the uterine endometrial tissues during the estrous cycle and pregnancy of all stages. Analysis by immunoblotting revealed that LPAR1 proteins were present in the porcine uterine endometrium during the estrous cycle and pregnancy. Immunohistochemical experiments demonstrated that LPAR1 protein was localized to endometrial epithelium and stromal cell, specifically to nuclei of these cell types. Results in this study show that LPAR1 is constitutively expressed in the uterine endometrium during the estrous cycle and pregnancy. These results suggest that LPA via LPAR1 may play a role in the uterine endometrial function throughout pregnancy in pigs.

ABSTRACT   INTRODUCTION   MATERIALS AND METHODS    Animals and Tissue Collection    Total RNA Extraction and Northern Blot Analysis    Protein Isolation and Western Blot Analysis    Immunohistochemical Analysis    Statistical Analysis   RESULTS    Levels of LPAR1 mRNA in the Uterine Endometrium during the Estrous Cycle and Pregnancy in Pigs    Levels of LPAR1 Proteins in the Uterine Endometrium during the Estrous Cycle and Pregnancy in Pigs    Localization of LPAR1 Protein in the Porcine Uterine Endometrium during the Estrous Cycle and Pregnancy and Conceptus   DISCUSSION   REFERENCES

• Heewon Seo(Division of Biological Science and Technology, and Institute of Biomaterials, Yonsei University)
• Mingoo Kim(Division of Biological Science and Technology, and Institute of Biomaterials, Yonsei University)
• Yohan Choi(Division of Biological Science and Technology, and Institute of Biomaterials, Yonsei University)
• Hakhyun Ka(Division of Biological Science and Technology, and Institute of Biomaterials, Yonsei University) Corresponding author