Section 10
Chapter 9,930

Ontogeny of a1- and b1-isoforms of Na+-K+-ATPase in fetal distal rat lung epithelium

O'brodovich, H.; Staub, O.; Rossier, B.C.

American Journal of Physiology 264: 137-43


ISSN/ISBN: 0363-6143
Accession: 009929579

Because immature, in contrast to mature, fetal lungs have ineffective Na transport, we wished to determine the ontogeny of Na+-K+-ATPase expression in fetal distal lung epithelium (FDLE). FDLE and fibroblasts (FLF) from 17- to 22-day gestational age fetal rats (term = 22 days) were grown in primary culture. Northern and slot-blot analyses utilizing isoform-specific cDNA probes determined that a1- (3.7 kb) and b1- (2.7, 2.3, and 1.9 kb) transcripts were present in FDLE at levels approximately fivefold higher than in FLF. a2-, a3-, or b2-isoforms of Na+-K+-ATPase were not detected. In 17-day gestational age FDLE, only small amounts of a1-mRNA levels were detectable, and there were [similar]10-fold less b1-isoform transcripts. By 20 days gestational age, the level of a1-transcripts roughly doubled, whereas b1-levels increased approximately sixfold. Thus, during the transition from the canalicular to saccular stages of lung development, FDLE have a differentially regulated surge in mRNA levels of a1- and b1-Na+-K+-ATPase isoforms and do not switch isoforms during lung development. Levels for both isoform transcripts then fell before birth, reaching values less than those seen for 17-day gestational age FDLE. FDLE vesicle Na+-K+-ATPase activity did not increase until 22 days gestational age. Reprinted by permission of the publisher. .

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