Study on receptor and mediator of Escherichia coli heat-sable enterotoxin II.

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To determine the enterotoxin activity of Escherichia coli heat-stable enterotoxin II, we established a new method using the mouse intestinal loop. We examined the biological properties of purified Escherchia coli heat-stable enterotoxin II (STII) using mouse intestinal loop assays. Recently, we purified hemolysin of Aeromonas sobria as an important enteric pathogen in travelers' dairrhoea, and examined the biological properties of purified hemolysin. Main results are according to the following.1. STII stimulated arachidonic acid metabolism in intestinal epithelial cells, resulting in the elevation of the level of prostaglandin EィイD22ィエD2. The prostaglandin synthesis inhibitors aspirin and indomethacin significantly reduced the secretion caused by STII. These results implicated prostaglandin EィイD22ィエD2 in he mechanism of action of STII.2. Treating the mouse intestinal with an inhibitor of CaィイD12+ィエD1-calmodulin-dependent kinase II(CaMKII) KN93, reduced the secretion caused by STII. CaMKII activity in mouse intestinal cells increased after exposure to STII. Theses results indicated that CaMKII involved in the mechanism of action of STII.3. Purified hemolysin possessed both cytotoxic activity against mammalian cells and enterotoxic activity.4. Hemolysin stimulated production of cyclic AMP by T84 cells and the cyclic AMP produced emerged in the culture supernatant.5. A cell-surface 66kDa glycoprotein was found to serve as a hemolysin receptor in the human intestinal cell line, Intestine 407 cells.