Some properties of purified Escherichia coli heat-stable enterotoxin II

Abstract

We examined the biological properties of purified Escherichia coli heat-stable enterotoxin H (STH) using mouse intestinal loop assays and compared these properties with those of heat-stable enterotoxin I (STI) and cholera toxin (CT). The action of STU over time differed from those of STI and CT. STH did not alter cyclic GMP or cyclic AMP levels in intestinal mucosal cells. Our results supported the idea that the mechanism of action of STII in inducing fluid secretion is different from the mechanisms of action of STI and CT. This hypothesis was further supported by the fact that an anti-STII neutralizing serum did not neutralize the activities of STI and CT. Subsequently, we examined the involvement of prostaglandins in the action of STlI. The level of prostaglandin E2 in the fluid accumulated as a result of the action of STU increased, and the prostaglandin synthesis inhibitors aspirin and indomethacin significantly reduced the response to STH. These results implicate prostaglandin E2 in the mechanism of action of STH.

Production of heat-stable enterotoxin II by chicken clinical isolates of Escherichia coli

“…However, Whipp found that STII can evoke a secretory response in infant mice and jejunal loops of rats when endogenous protease activity is blocked with trypsin inhibitor [22]. We have found similar results in the mouse intestinal loop assay in the presence of a protein inhibitor [9]. These findings show that the activity of STII is not species specific, but STII activity in the chicken intestine has not previously been examined.…”

“…The intestinal loop assay was performed using mice weighing 30-35 g and chickens weighing 70-80 g. The animals were anaesthetized with sodium pentobarbital, and the intestines were exposed through a midline incision. The intestinal lumen was rinsed three times with saline as described previously [9]. After the rinses, a series of ligated intestinal loops was created.…”

“…Antisera against purified STII were obtained by subcutaneous injection of purified STII conjugates with hemocyanin into rabbits as described previously [9].…”

“…HCI buffer (pH 7.5). Aprotinin (Bayer, Leverkusen, FRG) was added to block the endogenous protease of mouse intestine as de-scribed previously [9]. All of the samples induced fluid accumulation in the loops.…”

“…We raised antibodies that can neutralize the activity of purified STII but not those of LT and STI [9]. We therefore examined the production of STII by these chicken pathogenic E. coli strains using an anti-STII serum and determined the contribution of STII to chicken diarrhea disease.…”