RESPIRATORY PROPERTIES OF THE NEONATAL BLOOD OF THE COMMON BRUSHTAIL POSSUM (TRICHOSURUS-VULPECULA)

The respiratory properties of the blood ofa newborn marsupial the comm on brushtail possum (Trichosurus vulpecula of the family Phalangeridae ), have been examined. The O-2 equilibrium curves (OECs) under standar d conditions (36 degrees C and partial pressure of Co-2 [Pco(2)] = 42 mmHg) were right shifted, being to the right of the maternal curves. T he partial pressure of O-2 (Po-2) at which blood is 50% saturated with oxygen (P-50) under these conditions was 42 mmHg in the neonatal bloo d. All the neonatal OECs had a Hill plot bent at about 50% saturation, and the mean value of the Hill coefficient (nH) was 5.96 for the uppe r part of the curve, indicating aggregation of Hb tetramers or interac tion between adjacent tetramers. Apart from previous findings in anoth er marsupial (Macropus eugenii), the first of these properties had not been shown before in arty species, the second had not been shown befo re in any normal mammalian blood. At higher and lower Pco(2) (72 and 2 1 mmHg) the neonatal OECs were of the same shape and were also to the right of the maternal OECs under equivalent conditions. The Bohr effec t of the neonatal blood was lower than that of adult blood; the neonat al red blood cells were nearly all nucleated and contained four Hb typ es, each different from adult Hbs. In these respects it was characteri stic of embryonic blood and similar to the blood of the prenatal and n eonatal tammar wallaby of the family Macropodidae.