PARENT SESSION
Oocyte Development
92
THE AFFECT OF RETINOL ON SHEEP OOCYTE METABOLISM.
Livingston, Tracy1, Eberhardt, Dawn1, Godkin, James1, 1
ABSTRACT- Previous studies demonstrated that retinol administration to ewes, in combination with superovulation, and followed by natural service, resulted in embryos with improved developmental competence, in vitro. The purpose of the present study was to evaluate ovine oocyte metabolism and determine the affects of retinol on this process. Briefly, ewes were superovulated with FSH and treated with retinol or vehicle. Oocytes were removed from preovulatory follicles, denuded of cumulus cells, and subjected to metabolic measurements during early (0-3 hours), mid (9-12 hours), or late (21-24 hours) stages of in vitro maturation using hanging-drop procedures. The substrates, 5-3H glucose, 1-14C glucose and 6-14C glucose, 2-14C pyruvate, and 3,4-3H glutamine were used to examine metabolism. Results show that glucose metabolism through the glycolytic pathway changed from early to mid time periods (3.21 to 13.87 pmoles/oocyte/3hours; p ≤ .04), and early to late time periods (3.21 to 10.00; p ≤ .0001). Glucose oxidation through the Krebs cycle changed over time from an undetectable level at 0-3 hours to 1.06 pmoles/oocyte/3hours at 21-24 hours (p ≤ .05). Glucose metabolism via the pentose-phosphate pathway was highest during the early time period (7.47 pmoles/oocyte/3hours) and decreased to undetectable levels by 9-12 hours. Oxidative metabolism measured by glutamine showed no significant differences over all time periods. Pyruvate oxidation increased from 0-3 to 21-24 hours (3.05 to 3.13; p ≤ .02). The pentose-phosphate pathway appeared to be most active early and then declined afterwards. These results suggest that ovine oocytes use both glycolysis and oxidative pathways throughout the maturation process. Although oocytes from retinol-treated ewes metabolized 5-3H glucose at a lower numerical rate (4.69 ± 2.32) than control ewes (13.36 ± 2.31), these results were not statistically different (p ≤ .076).
KEY WORDS: oocyte, metabolism, retinol