Abstract
The activity of glucose 6-phosphate dehydrogenase was determined in mouse embryos during the first 5 days of development from the time of ovulation up to implantation. The activity decreased from 1.39 to 0.19 m[mu] moles of NADP [Nicotinamide adenine dinucleotide phosphate] reduced/hr./embryo from ovulation to implantation. The specific activity of the embryo on the 1st day was higher than specific activities reported for most other tissues.