Functional characteristics of the porcine colonic epithelium following transportation stress and Salmonella infection

Abstract

Objective. Stressful life events and infections contribute to gut disorders such as irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD). We used a pig model to analyse whether this could be linked to altered mediator sensitivity of the epithelial lining. Material and Methods. Uninfected control pigs or pigs with subclinical Salmonella (S.) typhimurium DT 104 infection were killed either without (ConRest, InfRest) or with prior 8-h transportation (ConTrans, InfTrans). Short-circuit current (Isc), tissue conductance (Gt) and release of mast cell mediators were monitored in isolated colonic epithelia mounted in Ussing chambers. Epithelia were exposed to histamine (100 µM, mucosally), substance P (SP; 1 µM, serosally), calcimycin A23187 (1 µM, serosally) and theophylline (10 mM, bilaterally). Transepithelial flux of histamine and colonic activities of histamine N-methyltransferase (HMT) and diamine oxidase (DAO) were determined. Results. S. infection decreased baseline Isc, Gt and histamine fluxes, while transportation had no effect on these values. Mucosal histamine increased Isc only in ConTrans pigs. This was not associated with increased mucosal-to-serosal flux of histamine but with a 2-fold increased DAO activity. Serosal SP increased Isc only in transported animals, but the increase was six times higher in ConTrans versus InfTrans pigs. Effectiveness of SP was not dependent on the release of histamine or prostaglandin D2. A23187 and theophylline elicited increases in Isc that were not different between treatments. Conclusions. Transportation stress facilitates secretory responses of the colonic epithelium to SP and luminal histamine. This is suppressed by subclinical S. infection. Effects of S. infection on porcine colon resemble, in part, the known effects of an oral S. endotoxin application.