Developmental differences in rabbit lung epithelial cell Na(+)-K(+)-ATPase.
Previous studies showed that ouabain-sensitive rubidium (86Rb+) uptake by rabbit lung epithelial cells increases at birth, followed by a more gradual postnatal increase, reaching adult values by age 30 days. To see whether these changes in ouabain-sensitive cation transport were the result of changes in Na+ pump number or turnover rate, we measured binding of [3H]ouabain and ouabain-sensitive 86Rb+ uptake by freshly isolated lung epithelial cells harvested from near-term fetal, newborn, and adult rabbits. Ouabain-sensitive 86Rb+ uptake by fetal cells was 1/4 that of newborn cells and 1/10 that of adult cells. The maximal number of ouabain binding sites (Umax) was the same for fetal and newborn cells but almost threefold greater for adult cells. Na+ pump turnover rate, determined from ouabain-sensitive 86Rb+ uptake and Umax, was four times greater in newborn and adult cells than it was in fetal cells. Thus the increase in 86Rb+ uptake at birth could be explained by an increase in Na(+)-K(+)-adenosinetriphosphatase (ATPase) turnover rate, whereas the postnatal increase in 86Rb+ uptake could be accounted for by an increase in the amount of Na(+)-K(+)-ATPase per cell.
Chapman
D L
DL
Department of Pediatrics, University of California, San Francisco 94143.
Widdicombe
J H
JH
Bland
R D
RD
D000375:Aging; D000818:Animals; D000831:Animals, Newborn; D004848:Epithelium / Q000201:enzymology; D005260:Female; D005333:Fetus; D007700:Kinetics; D008168:Lung / Q000196:embryology / Q000201:enzymology / Q000254:growth & development*; D010042:Ouabain / Q000378:metabolism; D011247:Pregnancy; D011485:Protein Binding; D011817:Rabbits; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase