SummaryThe interrelationship of 2,3aiphosphogIycerate {2,3-DPG) and P50 levels during the fetal and postnatal life were determined in two mammalian species which do not have a switchover of hemoglobin type at the end of their fetal development. In the guinea pig mnd rabbit, the 23.DPG levels remain low during fetal life and increase only after birth remaining elevated throughout adult life, The adult levels were reached at 2 days of age in the guinea pig and the 20th day in rabbit. Fetal P50 values increased only after birth, paralleling the rise in the 23-DPG. The rapidity of the postnatal rise in 23-DPG and decrease in P50 appears related to the maturity of the newborn animal at birth in these species.
SpeculationThe synthesis of 2,3-DPC during fetal life appears to be limited. This limitation may be due to the lack of substrate or the key enzyme, 2,3DPG mutase, during fetal development.Hemoglobin function appears clearly adapted to meet the different metabolic needs of the fetus and he adult in their respective environments. Efficient oxygen transport requires that hemoglobin both combine with oxygen at prevailing pressures and release it to tissues at pressures appropriate for metaboIism.Fetal development in a variety of species is accompanied by a switchover from fetal to adult hemoglobin synthesis (1, 2). This switchover is part of a process that enables the fetal red blood cel, to adapt to postnatal physiologic requirements. Another form of postnatal adaptation which occurs within the red b i d cell is the neonatal increase in 2,3-DPG synthesis (6,7). In order to further our understanding of the modulation of oxygen affinity along with the changes in 2,3-DPG during the adaptation from the intra-to the extrauterine environment, comparative studies were carried out in rabbits and guinea pigs during the perinatal period. These mammals were selected in order to evaluate the relationship of changes in oxygen artinity to the state of activity and maturation of the newborn animal. The goal was to determine pre-and postnatal changes in red blood cell oxygen aEXioity and concomitant levels of 2,3-DPG in both species.The rabbit and guinea pig are similar in many respects in that both lack a specific fetal type hemoglobin (1 I), their hemoglobins interact with 2,3-DPG (5), the effect of the pH on the unloading of oxygen from their blood is within the same range ( 131, and they are similar in size (14). However, these species differ in their length of gestation and state of maturity at birth. Rabbits that require 30 days of gestation are born blind, deaf, hairless, and helpless, and are confined to a "nest" for about 3 weeks. In contrast, guinea pigs that have a gestational period of 68 days are well developed, possess a full haircoat, and can run about and fend for themselves m n after birth.
MATERiALS AND METHODSNew Zealand White rabbits and Hartley breed guinea pigs were used for this study (17). Fetal blood, pooled from littermates, was obtained after Cesarean section during the last trimesler of the gestational ...
