PARENT SESSION

(W390) EFFECTS OF CULTURE MEDIA AND ENERGY SOURCES ON NUCLEAR MATURATION IN BOVINE CUMULUS-ENCLOSED OOCYTES.

Bilodeau-Goeseels, Sylvie¹, ¹ Agriculture and Agri-Food Canada, Lethbridge, AB, Canada

ABSTRACT- The objective of this work was to examine the influence of the culture medium and the presence of energy sources on spontaneous nuclear maturation and inhibition of maturation in bovine cumulus-enclosed oocytes (CEO) obtained from slaughterhouse ovaries and cultured in vitro. In the first set of experiments, CEO were cultured in Medium 199, minimum essential medium, M16, or synthetic oviduct fluid (SOF, all containing 3 mg/ml BSA) and also in SOF with no BSA. These media were used alone or supplemented with hypoxanthine (HYPO, 4 mM) or the adenylate cyclase activator forskolin (FSK, 100 M). After 21 h of culture the oocytes were fixed for evaluation of nuclear maturation. Significantly more CEO remained at the GV stage in M16 compared to other media. HYPO significantly increased the percentage of CEO remaining at the GV stage and decreased the percentage of CEO reaching metaphase II (MII) in M16 medium; however, the effect of FSK was similar in all media. The effects of energy sources on nuclear maturation in the presence or absence of HYPO or FSK were examined in CEO cultured in M16 salts+PVA. Glucose 0.5 and 5.5 mM, pyruvate 0.32 and 2.2 mM, lactate 3.3 mM and glutamine (1.3 mM) significantly reduced the percentage of CEO remaining at the GV stage compared to M16 salts with no energy sources. The percentages with the individual energy sources were not significantly different from the complete M16 medium. Only glutamine significantly increased the percentage of CEO at the MII stage compared to M16 salts. When CEO were cultured in M16 salts + HYPO, pyruvate (0.32 mM), lactate (3.3 mM) and glutamine (1.3 mM) significantly reduced the percentage of CEO remaining at the GV stage after 21 h of culture. There was no significant effect of any of the energy sources on the percentage of CEO at the MII stage in the presence of HYPO. When CEO were cultured in M16 salts + FSK, the addition of energy sources did not significantly affect the percentage of CEO remaining at the GV stage. However, glucose (0.5 mM), pyruvate (0.32 mM), lactate (3.3 mM) and glutamine (1.3 mM) significantly increased the percentage of CEO reaching metaphase I. In conclusion, bovine CEO can reach MII in a simple salt medium containing, either glucose, pyruvate or lactate. Glutamine is also stimulatory to nuclear maturation.

KEY WORDS: bovine, oocyte, meiosis, energy sources