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After maturation in vitro for 0, 6, 12, 18 or 24 h, the metabolism of radiolabelled glucose, glutamine, pyruvate and glycine by individual cattle oocytes was measured for 3 h. The metabolism of glucose through the Embden–Meyerhof (1.77–2.66 pmol per oocyte per 3 h) and pentose-phosphate (0.39–0.75 pmol per oocyte per 3 h) pathways was low and did not change over time. The oxidative metabolism of glucose carbon through the Krebs cycle was low throughout maturation, but increased significantly (P ≤ 0.05) at 6 h (0.41 pmol per oocyte per 3 h) and 18 h (0.69 pmol per oocyte per 3 h). Pyruvate, glutamine and glycine metabolism in the Krebs cycle increased during culture. Pyruvate metabolism increased significantly from 0 h (17.3 pmol per oocyte per 3 h) to 6 h (23.3 pmol per oocyte per 3 h) and reached a maximum at 12 h (30.8 pmol per oocyte per 3 h). Glutamine metabolism was unchanged from 0 to 12 h (0.89 pmol per oocyte per 3 h), and then increased significantly at 18 h (2.25 pmol per oocyte per 3 h). Glycine metabolism increased significantly from 6 h (0.21 pmol per oocyte per 3 h) to 12 h (0.46 pmol per oocyte per 3 h) and reached a maximum at 18 h (0.68 pmol per oocyte per 3 h). The results suggest that oxidative metabolism increases, and is the major site of cellular energy production, during maturation of the cattle oocyte in vitro.
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Summary. The metabolism of radiolabelled glucose and glutamine was measured in individual cattle embryos produced by in vitro maturation and fertilization of oocytes, and culture with bovine oviductal epithelial cells. Metabolism of glucose through the pentose-phosphate pathway increased almost 15 times and the total metabolism of glucose 30 times, during development from the two-cell to the expanded blastocyst stage. The first marked increase in glucose metabolism did not occur until between the eight- and 16-cell stages, the time of activation of the embryonic genome. Conversely, the metabolism of glutamine was high in two- and four-cell embryos and then decreased to reach a minimum at the compacted morula to blastocyst stage, possibly because of degradation of maternally derived enzymes. Blastocyst expansion was accompanied by significant increases in the metabolism of glucose and glutamine, presumably reflecting the increased energy demands of Na+–K+ ATPase necessary for formation and maintenance of the blastocoel.
Keywords: cattle; embryo; energy metabolism; development; glutamine
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Summary. Marked disparity in the uterine horn dimensions and relative degrees of caruncle development in suni suggested that exclusive or predominant dextral implantation occurs in association with bilateral ovulatory activity. Daily urinary measurements of pregnanediol-3α-glucuronide revealed an oestrous cycle of ∼21 days in length. Ovarian activity was controlled for synchronization of oestrus by using progestagen-impregnated intravaginal sponges and multiple ovulations were induced by using exogenous gonadotrophin therapy. An effective transcervical uterine catheterization technique was developed for the non-surgical collection of embryos. The efficiency of embryo recovery performed 5 days after sponge removal was 50·0%.
Keywords: suni; antelope; reproductive anatomy; placentation; oestrous cycle; superovulation; embryo collection
