SUMMARY
The Escherichia coli heat-stable enterotoxin (stb) is the most prevalent toxin associated with diarrheagenic E coli isolates of porcine origin. Unequivocal biological activity of this toxin has been observed only in swine intestine. In this study, when endogenous protease activity was blocked with soybean trypsin inhibitor, intestinal secretion was stimulated by stb in jejunal loops of rats, mice, calves, and rabbits. Compared with pigs, rats, mice, and calves, rabbits were relatively insensitive to stb. These data demonstrate that the activity of stb is not a speciesspecific toxic activity; there is species variation in sensitivity to stb, and some common laboratory animals may have potential to be used to measure biological activity of stb.
