Changes in uterine endometrial phospholipids and fatty acids throughout the oestrous cycle and early pregnancy in the ewe

This study examined changes in ovine endometrial phospholipids and fatty acid concentrations associated with luteolysis and the establishment of pregnancy in the ewe on days 3, 12 and 15, respectively. Results from this study indicate that endometrial lipids increased as the oestrous cycle progressed from days 3 to 12 and 15, whereas during early pregnancy, endometrial lipids decreased on day 15 of pregnancy when compared to days 3 and 12 of pregnancy. Phosphatidylcholine followed a similar pattern to that of total lipids, with an increase in phosphatidylcholine concentrations as the oestrous cycle progressed. During the early stages of pregnancy, phosphatidylcholine increased from day 3 to day 12, but then returned to previous levels by day 15 of pregnancy. Phosphatidylethanolamine increased late in the oestrous cycle, on day 15 as compared to days 3 and 12. This increase did not occur during early pregnancy, with phosphatidylethanolamine concentrations being constant from day 3 to day 15 of pregnancy. Both phosphatidylinositol and phosphatidylserine followed a similar pattern to phosphatidylethanolamine during the oestrous cycle and remained constant during early pregnancy. The fatty acid content of the major phospholipids involved in prostaglandin synthesis were examined over the range of fatty acids from C14:0 to C24:1omega9. Although changes in arachidonic acid were observed, there were no clear indications that these changes were directly related to the changes in PGF2alpha synthesis.