Absence of high blood oxygen affinity in the fetal cat

Abstract

Paired blood samples were obtained from maternal and fetal cats for the construction of oxygen-hemoglobin equilibrium curves at 38°C. The P 50 at a plasma pH of 7.40 and 38°C was 35.6 mm Hg for fetal blood and 36.2 mm Hg for maternal blood. The Bohr effect factors were 0.47 and 0.48 respectively. No differences were observed between adult and fetus in oxygen affinity of dialyzed hemoglobin solutions or on starch gel electrophoresis. Fetal cat blood has a higher P 50 than that observed in any other fetus and represents an exception to the general rule that fetal blood has a higher oxygen affinity than maternal blood when expressed at the same pH. The implications for placental gas exchange in this species are considered.