Adenylate energy charge and hemoglobin function in developing mouse embryos

1. Adenylate energy charge (EC) was measured in mouse embryos and showed a significant rise from 0.79 at day 11 of gestation to 0.87 at day 15 (P less than 0.05). 2. The low value of EC between days 11 and 13 corresponds with the predominance of the embryonic hemoglobin fraction E-I which has high affinity and poor cooperativity. 3. The highest value of EC corresponds with the predominance of adult hemoglobin which has lower affinity and cooperative oxygen binding. 4. Weight-specific oxygen uptake rates of isolated embryos decreases with weight gain and it is suggested that the energy charge is a manifestation of metabolic regulatory processes which sustain embryonic growth.