Expression of the epithelial Na+ channel in the developing rat lung
O'Brodovich, H.; Canessa, C.; Ueda, J.; Rafii, B.; Rossier, B.C.; Edelson, J.
American Journal of Physiology 265(2 Pt 1): C491-C496
1993
ISSN/ISBN: 0002-9513 PMID: 7690185 Document Number: 419104
The adult mature fetal, but not immature fetal, lung is capable of actively transporting Na+ from the alveolar space. The reason for the impaired Na+ transport in the immature lung is not known; however, the apical membrane Na+ channel is the rate-limiting step for epithelial Na+ transport. This study determined whether transcripts coding for the adult rat colonic epithelial Na+ channel (arENaC) were present in the fetal and adult lung and whether they were developmentally regulated. Similarly sized arENaC transcripts were identified in RNA isolated from fetal and adult whole rat lung, primary cultures of fetal and adult alveolar epithelium, and adult rat whole kidneys, suggesting that the lung arENaC is a similar transcript to that found in the salt-deprived rat colonic epithelium. There were low mRNA levels in 17- to 18-day gestational age (GA) fetal lungs and epithelium (term GA = 22 days), but these levels increased markedly during the saccular stage of lung development (20 days GA) and remained high in adult lungs. The combined administration of thyroid-releasing hormone and dexamethasone to pregnant rats between 16 and 18 days GA induced the expression of lung arENaC in their fetuses. We conclude that arENaC is expressed in mature fetal and adult alveolar epithelium and that it is influenced by hormones known to alter maturation of the fetal lung. Reprinted by permission of the publisher. .