Expression and localization of lung surfactant protein B in Eustachian tube
epithelium.
Paananen, Reija, Virpi Glumoff, Raija Sormunen, Wim Voorhout and Mikko Hallman.
1Biocenter Oulu, 2Department of Pediatrics, and 3Department of Pathology,
University of Oulu, 90014 Oulu, Finland; and 4Department of Biochemistry and Cell
Biology, Faculty of Veterinary Medicine, Utrecht University, ?? ???? Utrecht, The
Netherlands
APStracts 7:0245L, 2000.
Surfactant protein (SP) B is an essential component of the pulmonary surfactant complex,
which participates in reducing the surface tension across the alveolar air-liquid interface.
The Eustachian tube (ET) connects the upper respiratory tract to the middle ear, serving
as an intermittent airway between the pharynx and the middle ear. Recently, we described
the expression of SP-A and SP-D in the ET, suggesting their role in middle ear host
defense. Our present aim was to detect whether the expression of SP-B is evident in the
porcine ET. With Northern blot analysis, RT-PCR, and in situ hybridizations,SP-B
mRNA was identified and localized in the ET epithelium. The cellular localization of SP-
B was revealed with immunohistochemistry, electron microscopy, and immunoelectron
microscopy. The protein was found in the secretory granules of epithelial cells and also
attached to the microvilli at the luminal side of these cells. The SP-B immunoreactivity of
aggregates isolated from ET lavage fluid was similar to that isolated from
bronchoalveolar lavage fluid. We conclude that there are specialized cells in the ET
epithelium expressing and secreting SP-B and propose that SP-B may facilitate normal
opening of the tube and mucociliary transport.
Received 15 August 2000; accepted in final form 2 October 2000
APS Manuscript Number L293-0.
Article publication pending Am J Physiol Lung Cell Mol Physiol
ISSN 1080-4757 Copyright 2000 The American Physiological Society.
Published in APStracts on 7 November 2000