[Oxygen tension of preimplantation hamster embryos]

The intracellular oxygen tension in hamster embryos at various early stages of development was examined using a microelectrode technique. Changes in PO2 values before and after insemination in vitro were also investigated. The results were as follows. The oxygen tension in the culture medium was 83.8-99.0 mmHg. On the other hand, the mean oxygen tension in unfertilized oocytes was 51.1 +/- 7.3 mmHg (range 38.0-63.8 mmHg) and remained at these unfertilized levels throughout fertilization (49.6 +/- 7.1 mmHg). Slight but significant increases in oxygen tension in embryos occurred at the 2 cell stage and each successive stage. Mean values for PO2 in 2 cell, 4 cell and 6-8 cell stages were 58.5 +/- 5.6, 59.7 +/- 6.2 and 60.7 +/- 3.1 mmHg, respectively. These results suggested that the respiratory activity of oocytes seemed to be increased during the early cleavage stage and that this microelectrode technique should be useful in further studies of respiratory metabolism in oocytes and preimplantation embryos.