Phosphate Partition in the Erythrocytes of Normal Newborn Infants and Infants with Erythroblastosis Fetalis. III. P³² Uptake and Incorporation

The uptake and incorporation of P³²O₄ by the cord blood erythrocytes of normal and erythroblastotic infants and the erythrocytes of adults was studied by incubating specimens in ACD at 37 C. in air. The uptake of p³² from the plasma was slower in the infants than in the adults. It was possible to demonstrate an initial "fast" phase followed by a "slow" phase in all the plasma p³² uptake experiments. The half-value time and the percentage turnover per minute indicated greater activity in the adults compared to the infants. The balance of movement of phosphorus was from red cells to plasma in all the experiments. No striking differences in phosphate metabolism were demonstrated between the normal and erythroblastotic newborns, except for the large turnover in µM of P per minute by the red cells of the latter during the first 20 minutes of incubation.

Labeling of intraerythrocytic inorganic phosphorus (P_i), adenosine triphosphate (ATP) and 2,3-diphosphoglycerate (2,3-DPG) proceeded more slowly in the infants than in the adults. The labeling of the erythrocyte 2,3-DPG of all the infants lagged far behind P_i and ATP whereas in the adults the r.s.a. of 2,3-DPG had equalled or exceeded the r.s.a. of P_i and ATP in four hours. It is suggested that there is decreased synthesis of phosphoglycerates by the erythrocytes of the newborn which may be due to a lower level of glyceraldehyde-3-phosphate dehydrogenase activity.