Lipid and arachidonic acid accumulation in naturally regressing porcine corpora lutea

Patterns of luteal lipid and arachidonic acid accumulation were examined in relation to luteal progesterone and prostaglandin F synthesis in 30 sows and gilts between days 8 and 18 of the estrous cycle. Net in vitro release of progesterone from luteal tissue declined from 722 ng/100 mg tissue at day 8 to 81 ng/100 mg tissue at day 18. Although statistical significance was not present, net prostaglandin F release increased slightly from 8.6 to 13.9 ng/100 mg tissue. Luteal free cholesterol, esterified cholesterol, and free fatty acid contents did not change between days 8 and 18 whereas triglycerides accumulated rapidly between days 14 and 18 of the estrous cycle. Phospholipids increased between days 8 and 12, plateaued at 20.2 mg/g between days 14 and 16, and decreased to 15.4 mg/g on day 18. Between days 12 and 18, arachidonic acid increased from 19.4 to 34.8% in cholesterol esters, from 10.1 to 22.5% in triglycerides, and from 12.3 to 27.2% in luteal free fatty acids. Arachidonic acid in luteal phosphol lipids increased from 21.3 to 25.1% between days 14 and 16 of the estrous cycle. Luteal regression was associated with conservation of arachidonic acid. Based on blood plasma lipid fatty acid compositions, the corpus luteum elongated and desaturated essential fatty acids. Within porcine corpora lutea, calculated free arachidonic acid content was adequate for maintenance of prostaglandin synthesis.