Differential effects of polycationic protein on cl- secretory and
na& absorptive airways.
Smith, Michael D., Christopher M. Penland, and Michael R. Van Scott.
Department of Physiology, East Carolina University School of
Medicine, Greenville, NC
APStracts 3:0211L, 1996.
Effects of cationic proteins on electrolyte transport depend on the
specific channels and electrochemical driving forces expressed by
epithelia. The bioelectric responses of canine tracheal (CTE) and
bronchial epithelia (CBE) to a polycationic protein, protamine, were
therefore compared. CTE exhibited a brief transient inhibition of
short circuit current (Isc) followed by a prolonged increase of 18
[mu]A/cm2. The apical membrane transiently hyperpolarized then
depolarized by 11 mV. The increase in Isc was inhibited by
bumetanide. Cyclic AMP, ionomycin, and thapsigargin attenuated the
response whereas indomethacin or hypotonic solution had no effect
indicating that latent cystic fibrosis transmembrane regulator (CFTR)
Cl- channels were activated. CBE preparations exhibited a 4 [mu]A/cm2
decrease in Isc, 2 mV hyperpolarization of the apical membrane, and
an increase in fractional resistance of the apical membrane upon
exposure to protamine. These results were consistent with inhibition
of the Na& conductance in the apical membrane of CBE and confirmed
that polycationic proteins exert differential effects on Cl-
secretory and Na& absorptive airways.
Received 15 March 1996; accepted in final form 1 November 1996.
APS Manuscript Number L84-6.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996