Ion Transport Across Isolated Ileal Mucosa Invaded by Salmonella

The effects of two different invasive strains (TML and SL 1027) of Salmonella tryphimurium on Na and Cl transport in the absence of an electrochemical gradient were measured across rabbit ileal mucosa in vitro. Only strain TML elicits ileal fluid secretion in vivo. Net Na transport is negligible and net Cl secretion occurs across mucosae invaded by TML. In contrast, mucosae invaded by SL 1027 show absorption of both Na and Cl, as occurs in normal ileum. The luminal addition of glucose stimulates Na absorption without affecting Cl transport across ileum invaded by either strain. Theophylline stimulates Na transport across TML-invaded mucosa, causing net secretion, and enhances Cl secretion. Across SL 1027-invaded tissues, theophylline reverses spontaneous ion absorption, causing secretion of both Na and Cl. The data suggest that stimulation of active Cl secretion combined with inhibition of spontaneous Na absorption may account for the diarrhea of salmonella enteritis. However, invasion of the mucosa alone by S. typhimurium is not necessarily associated with major alterations in ion transport, suggesting that a factor, in addition to invasion, is necessary for fluid secretion. The effects of theophylline are compatible with strain TML exerting submaximal stimulation of cyclic adenosine monophosphate activity or involving another metabolic pathway which also inhibits spontaneous Na absorption and stimulates Cl secretion.