Segmental heterogeneity of rat colonic electrogenic secretion in response to the bacterial enterotoxin Escherichia coli STa in vitro.

The effects of the bacterial toxin Escherichia coli STa on electrogenic secretion in proximal, mid and distal rat colon were examined in vitro using the short-circuit current (Isc) as an index of secretion. All areas showed toxin-elevated Isc which was reduced by bumetanide. The proximal colon was the most sensitive (lowest ED50) but displayed the lowest maximal increase in Isc, the mid colon had the largest maximal electrogenic response while the distal colon proved to be the least sensitive (highest ED50). Atropine (1 microM) and tetrodotoxin (1.25 microM) reduced the maximum Isc response to STa by up to 42%, indicating that the enteric nervous system may be partly involved in the response.