Developmental regulation of na,k-atpase in rat lung.
Ingbar, David H., Cynthia Burns Weeks, Maureen Gilmore-Hebert, Eric
Jacobsen, Sara Duvick, Richard Dowin, S. Kay Savik, and James D.
Jamieson.
Department of Medicine, University of Minnesota, Minneapolis, MN.
and the Departments of Medicine and Cell Biology, Yale University
School of Medicine, New Haven, CT
APStracts 2:0198L, 1995.
Late in gestation lung epithelium changes from net chloride and fluid
secretion to sodium and fluid absorption. Fluid resorption is
required for postnatal gas exchange and occurs by combined action of
epithelial sodium channels and Na,K-ATPase. We hypothesized that
alveolar epithelial Na,K-ATPase increases perinatally.
Immunofluorescence (IF) and immunoelectron microscopy (IEM) with a
monoclonal anti-alpha subunit antibody demonstrated that Na,K-ATPase
was present on the basolateral surfaces of columnar epithelial cells
at fetal day (FD) 17 and on type II cells throughout development.
However, type I epithelial cells did not have detectable Na,K-ATPase.
The steady state levels of both the alpha 1 isoform and beta subunit
mRNAs were maximal at FD20-neonatal day (ND)1, with consistent
increases from the FD17 level. Na,K-ATPase alpha subunit protein also
increased from FD 17 to FD 20-22 and then decreased in the early
postnatal period. The ouabain-inhibitable sodium pump activity per mg
membrane protein increased 2.6 fold from FD17 to FD22-ND1 (p <
0.05). The quantities of sodium pump mRNA, antigenic protein and
enzyme activity increase in late gestation, in accord with a proposed
role for Na,K-ATPase in resorption of alveolar sodium and fluid in
preparation for birth.
Received 30 September 1993; accepted in final form 23 October
1995.
APS Manuscript Number L209-3.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95