BLOOD O-2 TRANSPORT IN NEWBORN AND ADULT OF A VERY SMALL MARSUPIAL (SMINTHOPSIS-CRASSICAUDATA)

Blood O-2 transport and hemoglobin types have been studied in a Dasyur id marsupial (Sminthopsis crassicaudata) at the neonatal (10-20 mg) an d adult (16 g) stages, and in part of the transition period. In neonat es the blood was embryonic in type with erythrocytes nucleated and con taining two Hb types both different from adult Hb. The oxygen equilibr ium curves (OECs) at day 1 had a P-50 of 38 mmHg at 36 degrees C and P -CO2 = 43 mmHg. This is lower than in other neonatal marsupials, but h igher than in fetal or neonatal eutherian mammals. Adult P-50 under th e same conditions was higher (59 mmHg), the normal relationship in viv iparous animals. Hill plots of neonatal OECs showed a sharp upward ben d at about 50% saturation. As in other embryonic and neonatal marsupia ls, in the upper part of the plot n(H) was greater than 4. This indica tes aggregation of Hb tetramers. The Bohr effect of neonatal blood at higher P-CO2 values (43-71 mmHg P-CO2) was zero. The special features of neonatal blood had largely disappeared by day 6.