SECRETORY PATHWAYS IN SALMONELLA TYPHIMURIUM-INDUCED FLUID ACCUMULATION IN THE PORCINE SMALL-INTESTINE

The involvement of 5-hydroxytryptamine (5-HT) and 5-HT3 receptors and prostaglandin E-2 (PGE(2)) in Salmonella Typhimurium-induced fluid acc umulation in the porcine small intestine was investigated. Salmonella Typhimurium (10(8) and 10(10) cfu) and cholera toxin (CT; 20 mu g) wer e instilled for 8 and 11 h in ligated loops in the porcine jejunum and ileum. Fluid accumulation and concentrations of Na+, K+, Cl-, 5-HT an d PGE(2) in the fluid accumulated in the loops were measured. The flui d accumulation was also measured when Salmonella Typhimurium (10(10) c fu) and CT (20 mu g) were instilled for 8 h in ligated loops in jejunu m and ileum in pigs given subcutaneous injections of saline or the 5-H T3 receptor antagonist ondansetron (200 mu g/kg). Salmonella Typhimuri um (10(10) cfu) and CT both induced fluid accumulation in jejunum and ileum after 8 and 11 h. Both treatments also induced an increase in lu minal release of 5-HT and PGE(2). The accumulated fluid was iso-osmoti c and hyperosmotic in CT- and Salmonella Typhimurium-treated loops, re spectively. Ondansetron reduced the Typhimurium-induced fluid accumula tion in both jejunum and ileum by c. 40%, while it failed to reduce th e response to CT. These results demonstrate that 5-HT and PGE(2) are r eleased and 5-HT3 receptors activated in the secretory pathway of Typh imurium in the porcine small intestine.