Electrolyte transport in rabbit cecum. I. Effect of RDEC-1 infection

Abstract

To investigate the characteristics of intestinal ion and fluid secretion induced by the adherent, effacing enteropathogenic Escherichia coli strain RDEC-1, we infected weanling rabbits with 10(7)-10(8) RDEC-1 organisms and then studied cecal ion transport under short-circuit conditions in Ussing chambers. Results in tissues with confluent adherent organisms were compared with those in uninfected ceca and in ceca stimulated with dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP). The short-circuited cecum normally absorbed Na and Cl, secreted bicarbonate (as represented by the residual ion flux), and displayed a high rate of nondiffusional Na and Cl transport. RDEC-1 infection did not alter the short-circuit current (Isc), but it increased the conductance (Gt), decreased the potential difference (PD), abolished net Na absorption, and reversed Cl absorption to secretion. The changes in Na and Cl net fluxes may be explained by inhibition of a Na-Cl linked absorptive process. In contrast, DBcAMP significantly increased the Isc, PD, and Gt, decreased net Na flux, and abolished net Cl absorption by stimulating electrogenic Cl secretion. These results suggest that RDEC-1-induced changes in cecal ion transport are not mediated by cAMP. The reduction in Na-Cl linked absorption is consistent with anatomic changes in the apical surfaces of absorptive epithelial characteristic of effacing enteroadherence, whereas the increased conductance is consistent with tight junction disruption seen with RDEC-1 infection.

Virulence Inhibition by Zinc in Shiga-Toxigenic Escherichia coli

“…The zinc levels achieved in the presence of active infection could be different from those we measured in uninfected rabbits. EPEC is known to induce a malabsorptive state in humans and animals (20,25), so it is possible that zinc absorption would be reduced during infection and that larger amounts of zinc would therefore reach the ileum, cecum, and colon. On the other hand, zinc concentrations could be reduced by the dilutional effect of diarrheal fluid secretion.…”

Adhesion and its role in the virulence of enteropathogenic Escherichia coli

“…The same strain also elicited changes in ion transport. Sodium absorption was abolished, and chloride absorption was reversed to secretion (197 …”

Rapid modulation of electrolyte transport in Caco-2 cell monolayers by enteropathogenic Escherichia coli (EPEC) infection

“…A reduction in absorptive capacity has been shown in intestinal tissues using rabbit models of EPEC infection15 16; however, malabsorption alone would not explain the rapid onset of diarrhoea (as early as three hours) reported in experimental human infections 17. This suggests the possibility of an EPEC induced secretory process, particularly in early infection.…”