Oxygen consumption by human oocytes and blastocysts grown in vitro

Oxygen consumption by human oocytes and blastocysts was analysed using a sensitive micro-spectrophotometric technique. Oocytes were obtained from women undergoing laparotomy for sterilization or hysterectomy, and blastocysts were obtained as spare embryos from the local in-vitro fertilization programme. There was no significant difference between oocyte oxygen consumption on the day of isolation and after 1 day of culture, 0.53 +/- 0.08 (n = 9) and 0.35 +/- 0.06 (n = 5) nl/h oocyte, respectively. Blastocyst oxygen consumption was measured after a culture period of 5-8 days after in-vitro fertilization. Mean oxygen consumption by healthy looking blastocysts was 0.34 +/- 0.03 (n = 15) nl/h blastocyst, and there was no change in oxygen consumption with culture time. This level of respiration was lower than expected, both when compared with the oocytes and when compared with levels reported for blastocysts of other species.