Composition of the Lipid Droplets of the Bovine Corpus Luteum

Abstract

2.Establishment and maintenance of pregnancy is dependent on progesterone synthesized by luteal tissue in the ovary. Our objective was to identify the characteristics of lipid droplets (LDs) in ovarian steroidogenic cells. We hypothesized that LDs are a major feature of steroidogenic luteal cells and store cholesteryl esters. Bovine luteal tissue was used for whole tissue analysis. Further analyses were performed on isolated ovarian steroidogenic cells: granulosa and theca cells of the follicle, and small/large luteal cells. Isolated luteal LDs were collected for lipid/protein analyses. Luteal tissue contained perilipins 2/3/5, hormone-sensitive lipase and abhydrolase domain containing 5. Luteal tissue was enriched in TGs compared to other tissues, except of adipose tissue. Large and small luteal cells were distinguished from follicular cells by the presence of LDs and LD-associated proteins. Furthermore, LDs from large luteal cells were numerous and small; whereas, LDs from small luteal cells were large and less numerous. Isolated LDs contained nearly all of the TGs and cholesteryl esters present in luteal tissue. Isolated luteal LDs were composed primarily of TG, with lesser amounts of cholesteryl esters, diglyceride and other phospholipids. Bovine luteal tissue LDs are distinct from LDs in other bovine tissues, including follicular steroidogenic cells.