Enteropathogenic E-coli attenuates secretagogue-induced net intestinal iontransport but not Cl- secretion

Enteric bacterial pathogens often increase intestinal Cl- secretion. Entero pathogenic Escherichia coli (EPEC) does not stimulate active ion secretion. In fact, EPEC infection decreases net ion transport in response to classic secretagogues. This has been presumed to reflect diminished Cl- secretion. The aim of this study was to investigate the influence of EPEC infection o n specific intestinal epithelial ion transport processes. T84 cell monolaye rs infected with EPEC were used for these studies. EPEC infection significa ntly decreased short-circuit current (I-sc) in response to carbachol and fo rskolin, yet I-125 efflux studies revealed no difference in Cl- channel act ivity. There was also no alteration in basolateral K+ channel or Na+-K+-2Cl (-) cotransport activity. Furthermore, net Cl-36(-) flux was not decreased by EPEC. No alterations in either K+ or Na+ transport could be demonstrated . Instead, removal of basolateral bicarbonate from uninfected monolayers yi elded an I-sc response approximating that observed with EPEC infection, whe reas bicarbonate removal from EPEC-infected monolayers further diminished I -sc. These studies suggest that the reduction in stimulated I-sc is not sec ondary to diminished Cl- secretion. Alternatively, bicarbonate-dependent tr ansport processes appear to be perturbed.