CHANGES IN THE METABOLISM OF GLUCOSE, PYRUVATE, GLUTAMINE AND GLYCINEDURING MATURATION OF CATTLE OOCYTES IN-VITRO

After maturation in vitro for 0, 6, 12, 18 or 24 h, the metabolism of radiolabelled glucose, glutamine, pyruvate and glycine by individual c attle 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-ph osphate (0.39-1.75 pmol per oocyte per 3 h) pathways was low and did n ot change over time. The oxidative metabolism of glucose carbon throug h the Krebs cycle was low throughout maturation, but increased signifi cantly (P less than or equal to 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. Pyruv ate metabolism increased significantly from 0 h (17.3 pmol per oocyte per 3 h) to 6 h (23.3 pmol per oocyte per S h) and reached a maximum a t 12 h (30.8 pmol per oocyte per 3 h). Glutamine metabolism was unchan ged 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 metaboli sm 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 (0.6 8 pmol per oocyte per 3 h). The results suggest that oxidative metabol ism increases, and is the major site of cellular energy production, du ring maturation of the cattle oocyte in vitro.