[Change in inorganic pyrophosphatase during maturation and aging of red blood cells from newborns]

The activity of inorganic pyrophosphatase (PPase) of red blood cells (rbc) from newborns is about 40% higher than that of adults. To answer the question whether the higher activity was due to the enhanced reticulocyte count of the newborn's cell population, the rbc of both newborns and adults were separated into different density subpopulations by means of isopycnic density gradient centrifugation in dextran. To judge the quality of separation in the individual age populations of rbc, the activity of glucose-6-phosphate dehydrogenase (G-6-PD) and the reticulocyte count were determined. The activity fall of PPase during maturation and aging of rbc is stronger than that of G-6-PD. The density subpopulations of rbc from newborns and adults with equal reticulocyte counts show the same PPase activities yet different G-6-PD activities. Obviously, the higher PPase activity of a cell population of newborns is due to the higher proportion of reticulocytes. The inorganic PPase is well suited as a guiding criterion to judge the maturity and age of rbc of newborns.