Interaction of luminal enterotoxin and low dose systemic endotoxin on small intestinal motility, secretion and permeability in the rat

We evaluated small intestinal motility, secretion, and mucosal permeability in fasted Sprague-Dawley rats following administration of luminal Escherichia coli heatstable enterotoxin (500 ng ml^-1) alone or in combination with intravenous endotoxin (100 μg kg^-1). Systemic endotoxin alone, or in combination with enterotoxin, caused a disruption of the regular interdigestive myoelectric complex as well as induction of spike bursts and diarrhea. Enterotoxin alone produced only minimal effects on intestinal myoelectric activity. Exposure of the intestine to systemic endotoxin and luminal enterotoxin in combination, led to a 2-fold increase in intestinal secretion in comparison with controls. This effect was significantly greater than the increase observed with enterotoxin (64±51%, P<0.05) or endotoxin alone (39±34%, P<0.001). Significant increase in intestinal permeability to luminal Evans blue was observed in intestinal loops exposed to systemic endotoxin (76±79%, P<0.05), but not to enterotoxin. Our data suggests that the secretory effects of luminal enterotoxin on the small intestine can be further augmented by endotoxin administered intravenously, which also results in increased intestinal mucosal permeability and a diarrheogenic motility pattern.