INTESTINAL ADAPTATION TO CYCLIC AMP‐MEDIATED HYPERSECRETION INDUCED BY THE HEAT‐LABILE ENTEROTOXIN OF VIBRIO CHOLERAE AND ESCHERICHIA COLI

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Abstract
Adaptation to cholera toxin (CT) and the heat-labile enterotoxin (LT) from E. coli was studied in vivo in the rat small intestine. Repeated peroral pretreatment with CT or LT induced protracted inhibition of the intestinal fluid response to these toxins. The CT-induced mucus release from intestinal goblet cells was not influenced by CT pretreatment; the binding of CT to the epithelium remained intact. The adenylate cyclase activity, which mediates CT and LT action, was repressed, as judged from the response of this enzyme to CL, LT and prostaglandin E1. Evidently, protection against CT and LT acquired in the gut is achieved by desensitization of the adenylate cyclase system.