Metabolism of glucose, pyruvate, and glutamine during the maturation of oocytes derived from pre-pubertal and adult cows

The aim of the study was to compare the energy metabolism of oocytes from pre-pubertal (2 to 3 months) and adult cows during maturation, to identify the cause of poor developmental potential in many pre-pubertal oocytes. The metabolism of [5-(3)H] glucose, [2-(14)C] pyruvate, and [G-(3)H] glutamine was measured at 0 hr, 12 hr, and 24 hr maturation. Oxidative metabolism was important during maturation of oocytes from both pre-pubertal and adult cows, with pyruvate metabolism peaking at 12 hr and glutamine metabolism increasing linearly and peaking at 24 hr. Peak oxidative metabolism was significantly lower in oocytes from pre-pubertal animals, for both pyruvate and glutamine (P < 0.05). Glucose metabolism increased significantly during oocyte maturation in both groups (0hr to 24 hr). Glucose metabolism was significantly lower in oocytes from pre-pubertal cows at 12 hr (P < 0.05). Oocytes from pre-pubertal animals were significantly smaller than oocytes from adult cows at 0 hr, 12 hr, and 24 hr maturation (P < 0.05). When metabolic rates were corrected for oocyte volume, there were no significant differences in substrate metabolism between oocytes from pre-pubertal and adult cows. There was however, a delay in the increase in glucose metabolism in pre-pubertal oocytes 0 hr to 12 hr maturation. Germinal vesicle breakdown was slower in oocytes from pre-pubertal animals with more oocytes still at the germinal vesicle stage approximately 5 hr post-aspiration, compared to oocytes from adult cows (P < 0.05). By 24 hr, development to metaphase II was equivalent for pre-pubertal and adult oocytes. This study identified differences in energy metabolism, oocyte size, and meiotic progression between the oocytes from pre-pubertal and adult cows that may account for the poor developmental potential of many pre-pubertal oocytes.