Intestinal barrier to intact horseradish peroxidase in experimental secretory diarrhea

Intestinal permeability to intact horseradish peroxidase (HRP, MW 40,000) was assessed during the acute phase of secretory diarrhea. Secretion was either induced in ligated loops of rabbit jejunum with cholera toxin or mimicked in vitro with db-cAMP, 8Br-cGMP, or theophylline in isolated fragments of rabbit jejunum mounted in Ussing chambers. Although intestinal electrolyte secretion was obtained under these conditions, as shown by the rises in short-circuit current and potential difference, jejunal permeability to HRP did not change. These results suggest that, throughout the time course of secretory diarrhea, no change occurs in the functional ability of the jejunal epithelium to protect the organism against massive intact protein penetration.