Chapman D L, Widdicombe J H, Bland R D
Department of Pediatrics, University of California, San Francisco 94143.
Am J Physiol. 1990 Dec;259(6 Pt 1):L481-7. doi: 10.1152/ajplung.1990.259.6.L481.
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.
先前的研究表明，兔肺上皮细胞对哇巴因敏感的铷（86Rb+）摄取在出生时增加，随后在出生后逐渐增加，到30日龄时达到成年水平。为了观察哇巴因敏感的阳离子转运变化是否是钠泵数量或周转率变化的结果，我们测量了从近足月胎儿、新生兔和成年兔新鲜分离的肺上皮细胞对[3H]哇巴因的结合以及哇巴因敏感的86Rb+摄取。胎儿细胞对哇巴因敏感的86Rb+摄取量是新生细胞的1/4，是成年细胞的1/10。胎儿和新生细胞的哇巴因结合位点最大数量（Umax）相同，但成年细胞的几乎大三倍。根据哇巴因敏感的86Rb+摄取和Umax确定的钠泵周转率，新生细胞和成年细胞是胎儿细胞的四倍。因此，出生时86Rb+摄取的增加可以用钠钾腺苷三磷酸酶（ATP酶）周转率的增加来解释，而出生后86Rb+摄取的增加可以用每个细胞中钠钾ATP酶量的增加来解释。
