Action of Escherichia coli Enterotoxin: Adenylate Cyclase Behavior of Intestinal Epithelial Cells in Culture

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Heat-labile enterotoxin preparations obtained from two enteropathogenic strains of Escherichia coli of porcine and human origin were shown to stimulate adenylate cyclase activity of human embryonic intestinal epithelial cells in culture. Comparable results were also obtained when cholera toxin was used. The degree of enzyme stimulation was proportional to the concentration of enterotoxin. Similar preparations from two strains of non-enterotoxigenic E. coli had no effect on adenylate cyclase activity. Cells exposed to enterotoxin could be washed after 1 min of contact time without altering the subsequent course of maximum adenylate cyclase activity, which was maintained for at least 18 h at 37 C. During long periods (18 h) of tissue culture incubation, the determination of adenylate cyclase activity was 200- to 300-fold more sensitive than quantitating fluid accumulation in the adult rabbit ileal loop model. Decreasing the incubation time appreciably reduced the sensitivity of the epithelial cells to enterotoxin. E. coli enterotoxin is an effective activator of nonintestinal adenylate cyclase systems. Treatment of KB and HEp-2 cell lines with enterotoxin also resulted in significant enzyme stimulation. The intestinal epithelial cell tissue culture model provides a sensitive homogenous biological system for studying the response of intestinal adenylate cyclase to enterotoxin while eliminating the numerous cellular and tissue components present in the ligated ileal loop model.

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