EXPOSURE OF THE LATERAL ENTEROCYTE MEMBRANE BY DISSOCIATION OF CALCIUM-DEPENDENT JUNCTIONAL COMPLEX AUGMENTS ENDOCYTOSIS OF ENTERIC BACTERIA

Intestinal bacterial translocation is facilitated in a variety of clin ical conditions involving increased intestinal permeability, such as s hock and trauma. Because there is both in vivo and in vitro evidence t hat enteric bacteria can be internalized by intestinal epithelial cell s, experiments were designed to test the effect of increased intestina l permeability on enterocyte endocytosis of enteric bacteria. Mature, confluent cultures of HT-29 enterocytes were placed in a calcium-free solution for 1 h. Enterocyte viability was not noticeably altered, but transepithelial electrical resistance was significantly decreased (in dicating a decrease in epithelial junctional integrity), and the enter ocytes were pulled apart. Electron microscopic observations revealed e nteric bacteria preferentially adherent on the exposed enterocyte late ral surface, and the numbers of viable enteric bacteria (Listeria mono cytogenes, Salmonella typhimurium, Proteus mirabilis, Escherichia coli , and Enterococcus faecalis) internalized by these enterocytes were si gnificantly increased. Restoration of calcium restored confluency to e nterocyte cultures, and bacterial internalization reverted to control levels. Thus, calcium-dependent junctional integrity might play a role in augmenting bacterial translocation in clinical conditions associat ed with increased intestinal permeability.