Tannin stimulates arachidonic acid release from bovine tracheal
epithelial cells.
Cloutier, Michelle M., and Linda Guernsey.
Pediatric Pulmonary Division, University of Connecticut Health
Center
APStracts 2:0208L, 1995.
Condensed tannin, isolated from cotton bracts extract (CBE), increases
arachidonic acid (AA) release from rabbit alveolar macrophages and
inhibits its subsequent reacylation. We determined whether tannin
from CBE had any effect upon arachidonic acid release in bovine
tracheal epithelial cells (BTE). 14C-AA release was measured at timed
intervals after addition of various concentrations of tannin to BTE
cells grown to confluence in the presence of 14C-AA. Tannin caused a
time and dose-dependent release of AA from airway cells with a
maximum release occurring at 1 minute in the presence of 100 [mu]g/ml
of tannin and was confirmed by high pressure liquid chromatography.
The pattern of release was similar to that observed with bradykinin
(2 x 10-6 M). AA release by tannin was partially inhibited by
indomethacin (10-5 M) but not by 5,8,11,14-eicosatetraynoic acid
(ETYA,10-5 M). Both of these drugs were effective in inhibiting
bradykinin-induced AA release. In addition, AA release was not
inhibited by cycloheximide. Endotoxin at 100 pg/ml and higher also
caused a time-dependent release of AA which was not inhibitable by
indomethacin or ETYA. Tannin-induced AA release was inhibited by
pretreatment with pertussis toxin but not by neomycin, an inhibitor
of phospholipase C (PLC). Neither pertussis toxin nor neomycin had
any effect upon endotoxin-induced AA release. In other experiments,
neither tannin nor endotoxin had any effect on 14C-AA uptake by BTE.
These data demonstrate that tannin at low concentrations and
endotoxin at high concentrations increase AA release by BTE cells.
The AA released by tannin is partially metabolized by the
cyclooxygenase pathway. We hypothesize that tannin induced AA release
is not mediated by PLC but may be mediated by other phospholipases
(PL) including PLA2.
Received 24 January 1994; accepted in final form 29 October 1995.
APS Manuscript Number L25-4.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 November 95