Changes in the metabolism of glucose, pyruvate, glutamine and glycine during maturation of cattle oocytes <i>in vitro</i>

Abstract

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 < or = 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.