AJP - Lung Cellular and Molecular Physiology, Vol 268, Issue 2 270-L277, Copyright © 1995 by American Physiological Society
Bioelectric properties of cultured monolayers from epithelium of distal human fetal lung
P. M. Barker, R. C. Boucher and J. R. Yankaskas
Department of Pediatrics, University of North Carolina at Chapel Hill 27599-7220.
Throughout intrauterine life, Cl(-)-rich liquid is secreted by the
pulmonary epithelium. To evaluate the role of the most distal epithelium in
liquid secretion, we measured bioelectric properties of monolayers composed
of epithelial cells from acinar structures of postmortem human fetal lung
(mean gestation, 22.3 wk; range, 18-24 wk). These monolayers formed
high-resistance (R) barriers (mean R = 363 Ohm/cm2) when cultured in
hormone-supplemented, serum-free medium. The transepithelial electrical
potential difference (4.0 mV, lumen negative), was similar to that of whole
fetal sheep lung in vivo. Equivalent short-circuit current (Ieq) was
inhibited by apical amiloride (-20%), 5-(N-ethyl-N-isopropyl)-amiloride
(-33 to -49%), or diphenylamine-2-carboxylate (DPC; -26%), and by
basolateral ouabain (-77%), whereas apical
4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) had no effect.
Bumetanide added to the basolateral bath did not affect resting Ieq, but
inhibited Ieq (-19%) in monolayers pretreated with apical amiloride,
basolateral terbutaline, and apical ATP, and also inhibited Ieq (-22%) of
monolayers pretreated with basolateral amiloride and DIDS. Ieq was
stimulated by terbutaline (90-128%), ATP (70-186%), and ionomycin (141%).
Stimulation of Ieq by these agents is compatible with induction of Cl-
secretion through two pathways: channels that are opened by a rise in
adenosine 3',5'-cyclic monophosphate, and channels that are opened by a
rise in intracellular Ca2+. Inhibition of Ieq by apical DPC implies that
Cl- secretion may contribute to basal Ieq.
