Blood O 2 transport in newborn and adult of a very small marsupial ( Sminthopsis crassicaudata)

Abstract

Blood O 2 transport and hemoglobin types have been studied in a Dasyurid marsupial ( Sminthopsis crassicaudata) at the neonatal (10–20 mg) and adult (16 g) stages, and in part of the transition period. In neonates the blood was embryonic in type with erythrocytes nucleated and containing two Hb types both different from adult Hb. The oxygen equilibrium curves (OECs) at day 1 had a P 50 of 38 mmHg at 36°C and P CO 2 = 43 mmHg. This is lower than in other neonatal marsupials, but higher than in fetal or neonatal eutherian mammals. Adult P 50 under the same conditions was higher (59 mmHg), the normal relationship in viviparous animals. Hill plots of neonatal OECs showed upward bend at about 50% saturation. As in other embryonic and neonatal marsupials, in the upper part of the plot n H was greater than 4. This indicates aggregation of Hb tetramers. The Bohr effect of neonatal blood at higher P CP 2 values (43–71 mmHg P CO 2 ) was zero. The special features of neonatal blood had largely disappeared by day 6.