Energy substrate requirement for in vitro maturation of oocytes from unstimulated adult rhesus monkeys

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Abstract
The energy substrates lactate, pyruvate, and glucose were evaluated for supporting in vitro cytoplasmic maturation of rhesus monkey oocytes. A total of 321 cumulus–oocyte complexes (COCs) aspirated from ≥ 1000 μm diameter follicles of unstimulated adult monkeys were matured in one of six media with various individual or combinations of energy substrates: (1) mCMRL‐1066 (control); (2) HECM‐10 (containing 4.5 mM lactate); (3) HECM‐10+0.2 mM pyruvate; (4) HECM‐10 + 5.0 mM glucose; (5) HECM‐10+ 0.2 mM pyruvate + 5.0 mM glucose; and (6) HECM‐10 minus lactate + 5.0 mM glucose. All media contained gonadotropins, oestradiol, and progesterone. Following maturation, all mature oocytes were subjected to the same in vitro fertilization and embryo culture procedures. Oocytes matured in control medium or in treatment groups 4 and 6 had the best morulae+ blastocysts developmental responses (35, 36, and 32%, respectively, P < 0.05). HECM‐10 + 0.2 mM pyruvate + 5.0 mM glucose for COC maturation supported intermediate embryonic development (16% morulae + blastocysts). The lowest (P < 0.05) morula + blastocyst developmental responses were obtained after maturation of COCs in HECM‐t10 and HECM‐10 + 0.2 mM pyruvate (4 and 6%, respectively). The COCs matured in glucose‐containing medium showed greater levels of cumulus expansion than those in glucose‐free medium. These results indicate that (a) glucose is both necessary and sufficient as the energy substrate for supporting optimal cytoplasmic maturation in vitro of oocytes from unstimulated rhesus monkeys; (b) pyruvate suppresses the stimulatory effect of glucose on oocyte maturation; (c) glucose is involved in cumulus expansion; (d) cumulus expansion is not a reliable indicator of primate oocyte competence. Mol. Reprod. Dev. 58:348–355, 2001.