Respiratory Metabolism of Mammalian Eggs. ∗

Abstract

Summary

Respiration of fertilized rabbit eggs (intact, punctured or dissected) in different pre-implantation stages was measured in the Cartesian diver and Warburg apparatus. Average O₂ uptake of eggs 16, 40, 65, 90, 120, 140 and 160 hr post-coitum was 0.61, 0.51, 0.48, 2.56, 200, 400 and 800 mμl/ovum/hr respectively. The high respiratory rate of blastocysts was associated with the morphological changes yet the rate of increase was not directly proportional to cell mass increase. It is suggested that these pacts reflect a change in metabolic pathways. Intact blastocysts (in Warburg) respire at a lower rate than punctured ones due to the bicarbonate content of blastocyst fluid which raised the pH in the CO₂-free atmosphere. Cumulus cells respire at a high rate while the zona pellucida does not respire at all.