Effect of Shigella enterotoxin on electrolyte transport in rabbit ileum

Shigella dysenteriae I is one of several bacteria which produces an enterotoxin capable of stimulating intestinal water and electrolyte secretion. Unlike cholera and Escherichia coli enterotoxins which have been shown to increase intracellular cyclic adenosine monophosphate levels in the small intestine, the mechanism by which shigella enterotoxin causes intestinal secretion is not known. To study shigella enterotoxin stimulated intestinal secretion, rabbit ileal mucosa exposed in vivo to Shigella dysenteriae I enterotoxin was studied in vitro in a modified Ussing chamber. Fluid and electrolyte accumulation occurred in vivo and net sodium secretion was present in vitro in the enterotoxin exposed tissue in contrast to net sodium absorption in control mucosa. Short circuit current (Isc) was similar in shigella enterotoxin exposed tissue compared with control tissue. The increase in Isc following addition of either theophylline or dibutyryl cyclic adenosine monophosphate was similar in enterotoxin exposed and control mucosa. The addition of glucosa resulted in a smaller increment of Isc in shigella enterotoxin treated tissue. Mucosal cyclic adenosine monophosphate levels in enterotoxin exposed mucosa did not differ from those of control. These results indicate that the characteristics of rabbit ileal mucosa exposed to shigella enterotoxin and cholera enterotoxin markedly differ, although both produce electrolyte secretion both in vivo and in vitro. These studies further suggest that, in contrast to its role in cholera enterotoxin induced intestinal secretion, cyclic adenosine monophosphate may not be the mediator of shigella enterotoxin stimulation of intestinal fluid and electrolyte secretion.