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Rebecca E. Spindler1 *, David E. Wildt1 *
Conservation and Research Center, National Zoological Park, Smithsonian Institution, Front Royal, VA 22630 1
Both in vitro matured (IVM) and in vivo matured (IVOM) domestic cat oocytes readily complete nuclear maturation, but IVM cumulus/oocyte complexes (COCs) have inferior developmental potential and altered metabolism compared with IVOM COCs. Even IVM COCs that have completed nuclear maturation (metaphase II [MII]) metabolize less glucose through glycolysis and oxidation than MII IVOM oocytes. The objective of this study was to determine if this difference in metabolism was indicative of oocyte developmental potential. Ovaries (12 pairs) stored in PBS at 4oC for < 6 h were minced with a scalpel blade to recover oocytes. Twenty high quality oocytes were subjected to IVM (32 h), and a section of cumulus was removed from each oocyte. Oocytes were denuded, and oocytes and cumulus cell samples were rinsed separately in medium containing 1 mM each of glucose (0.005 mM D-[5-3H]glucose and 0.995 mM D-[6-14C]glucose), pyruvate, lactate, glutamine and palmitate. Individual oocytes and cumulus samples were incubated in 3 l of this medium in the lid of a 1.5 ml Eppendorff centrifuge tube over a 25 mM NaHCO3 trap (38oC, 3 h). Oocytes then were individually inseminated with conspecific sperm, cultured in G1/G2 media at 38oC for 7 days and stained to determine cell number. Protein content of cumulus cell samples was analyzed using The Biorad Protein Assay. There were significant correlations between embryo development (cell number after 7 days culture) and (1) oocyte glycolytic activity (r2 = 0.63; p < 0.01) and (2) oocyte glucose oxidation (r2 = 0.70; p < 0.01). There was no correlation between individual oocyte development and cumulus cell glycolysis (r2 = 0.28; p > 0.05), or or oxidation (r2 = 0.17; p > 0.05). Thus, oocyte but not cumulus cell metabolism after IVM appears to indicate oocyte capacity for successful fertilization and development in vitro.
This abstract is being presented on Monday, August 2 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.