Developmental changes in erythrocyte Na+,K+ATPase subunit abundance and enzyme activity in neonates

Abstract

Aim - To study the relation between erythrocyte Na+,K+-ATPase subunit isoform composition, Na+,K+-ATPase activity, and cation pump function in preterm and term neonates. Design - Erythrocyte Na+,K+-ATPase subunit isoform abundance, Na+,K+-ATPase activity, and cation pump function were studied in blood samples obtained from 56 preterm neonates of 28-32 weeks gestation (group 1), 58 preterm neonates of 33-36 weeks gestation (group 2), and 122 term neonates (group 3) during the first two postnatal days. Results - α1 isoform abundance was higher and β2 isoform abundance was lower in group 1 than in group 3 (p = 0.0002). α2 and β1 isoform abundance did not change with maturation and there was no evidence for the presence of the α3 isoform. Gestational age was inversely related to Na+,K+-ATPase activity (p = 0.0001) and directly related to intracellular Na+ concentration (p = 0.0025). Conclusions - Expression of the α1 and β2 Na+,K+-ATPase subunit isoforms is developmentally regulated. The increased abundance of α1 isoforms of immature neonates translates to increased ATPase activity. The lower intracellular Na+ concentration of immature neonates suggests that their erythrocyte Na+,K+-ATPase cation pump function may also be increased.