Abstract
1. Neonatal rabbit blood exhibits a higher oxygen affinity than the maternal one and the difference gradually disappears as the postnatal age develops. The circumstance is also ascertained in the hemoglobin solution prepared from the fetal and maternal blood and the difference shows little alteration after the 20 hours' dialysis against deionized water in one and common vessel. No significant difference can be verified in the magnitude of heme-heme interaction between both kinds of hemoglobin irrespectively of their environments.
2. Minor but distinct differences are found between the fetal and adult oxyhemoglobins in the alkali denaturation behavior and the ultraviolet absorption spectrum and the dissimilarities disappear as the postnatal growth proceeds.
3. Starch-gel electrophoresis of both the adult and fetal carboxy-hemoglobins showed single homogeneous zone of the same mobility.
4. p-Chloromercuribenzoate titer per mole of the fetal oxy-hemoglobin is estimated as 2.2 and it increases gradually along with the postnatal development, reaching the figure of 3 or so in the adult ones.
5. These results are discussed in the light of previous investigations, and it is concluded that fetal and adult rabbit hemoglobin differ in physiological function as well as molecular structure. Contrary to human fetal and adult hemoglobins, the structural differences appear to be responsible for the distinction in the physiological function.
