Effect of Escherichia coli heat-stable enterotoxin on cell volume and intracellular inorganic ions of rat intestinal cells.

1.--Electron micrographs of rat jejunum mucosa incubated for 1 h in the presence of Escheria coli heat-stable enterotoxin (STa) in the lumen shows alterations of villous cells as well as of crypt cells. The brush border of mature enterocytes is partially desintegrated and covered with a thick mucus. Crypts are occupied on half of their height by cells very similar to Paneth cells, loaded with numerous large dark inclusions. 2.--Cell volume and intracellular inorganic ion concentrations have been estimated in mucosal scrapings of jejunum sacs, incubated in vitro for 1 or 3 h. The quick action (1 h of incubation) of STa is a swelling of the intestinal calls accompanied by an increase in Na+, Cl- and Ca2+ intracellular concentrations and a decrease in the K+ and Mg2+ ones. The delayed action (3 h of incubation) is an increase of extracellular space and a decrease in cell volume; and at the same time the intracellular concentration of Na+, Cl-, K+, Ca2+ and Mg2+ is augmented. 3.--After 3 h of incubation intestinal cells from the other levels of intestine (duodenum, ileum and colon) show the same variations in cell volume and intracellular inorganic ion concentrations under the influence of STa, as those recorded in the jejunum. 4.--The present work favours the hypothesis that all intestinal cells, villous or cryptic, are involved in the alteration of fluid ion transport ending in diarrhea.