Postnatal regulation of oxygen delivery: control of erythropoiesis following birth in dogs.

Blood hemoglobin concentration decreases during the first postnatal month of canine life. Red cell production, as indicated by reticulocyte levels, decreases following birth and does not increase until the second postnatal month. Bleeding and transfusion studies were performed to determine if the canine erythropoietic system is defective during this early neonatal period or is operating at a less than maximal rate due to adequate oxygen delivery to those tissues which regulate erythropoiesis. There is no fundamental defect in the erythropoietic system since bleeding stimulated reticulocyte formation during the first postnatal month. Conversely, the reticulocytosis that normally occurs during the second postnatal month was suppressed when oxygen delivery was increased by a red cell transfusion. We conclude that adequate oxygen delivery following birth causes a reduction in red cell production and results in postnatal anemia. Due to increasing metabolic oxygen requirements of continued growth, the blood oxygen delivery becomes inadequate by the second postnatal month and red cell production is stimulated.