Infect. Immun., Mar 1995, 745-750, Vol 63, No. 3
BA Harville and LA Dreyfus
The intestinal secretory action of Escherichia coli heat-stable enterotoxin
B (STb) is poorly defined. Previous work indicates that STb causes loss of
intestinal fluid and electrolytes by a mechanism independent of elevated
levels of cyclic nucleotides, the hallmark of other E. coli cytotonic
enterotoxins. In the work described in this report, we observed that
treatment of ligated rat intestinal loops with purified STb of E. coli
resulted in a dose-dependent rise in intestinal secretion concomitant with
dose-related increases in levels of serotonin (5-hydroxytryptamine [5-HT])
and prostaglandin E2 (PGE2). Treatment of rats with the 5-HT2 receptor
antagonist ketanserin prior to STb challenge resulted in significant (P
< 0.05) reduction in intestinal secretion. Blockage of 5-HT2 receptors
with ketanserin also reduced (P < 0.05) the level of PGE2 observed
following STb treatment, indicating that at least a portion of the PGE2 was
formed in response to 5-HT2 receptor stimulation. In a similar fashion,
indomethacin, an inhibitor of cyclooxygenase activity, significantly
reduced the level of secretion (P < 0.05) observed following STb
treatment yet had no effect on 5-HT levels. Treatment of rats with both
ketanserin and indomethacin further reduced STb-mediated secretion to a
level not attained by either drug alone. Taken together, our data suggest
that secretion due to STb involves both 5-HT and PGE2 as intestinal
secretagogues. Furthermore, PGE2 formation appears to arise through both
5-HT-dependent and 5-HT-independent pathways.
Copyright © 1995, American Society for Microbiology
Involvement of 5-hydroxytryptamine and prostaglandin E2 in the intestinal secretory action of Escherichia coli heat-stable enterotoxin B
Division of Cell Biology and Biophysics, School of Biological Sciences, University of Missouri-Kansas City 64110.
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