Lanthanum inhibition of Vibrio cholerae and Escherichia coli enterotoxin-induced enterosorption and its effects on intestinal mucosa cyclic adenosine 3',5'-monophosphate and cyclic guanosine 3',5'-monophosphate levels

Abstract

Several trivalent cations, including lanthanum (La3+), inhibited the secretion (enterosorption) induced by the enterotoxins of Vibrio cholerae and Escherichia coli in the rabbit ileum in vivo. High concentrations (>10 mM) of La3+ were required to inhibit cholera enterotoxin (CE)-induced enterosorption, probably because of the adsorption of the La3+ to mucus and its precipitation by HCO3-. Exposure to lower concentrations of La3+ often potentiated the CE-induced enterosorption. If luminal La3+ exposure followed CE exposure, some recovery of the enterosorptive response was observed. The longer the lag between the CE exposure and the La3+ exposure, the greater was the recovery of the enterosorptive response. Lanthanum inhibited HCO,secretion more than Clsecretion.

Pathophysiological effects of Vibrio cholerae and enterotoxigenic Escherichia coli and their exotoxins on eucaryotic cells.

“…Activation by CT in the presence of 10 mM magnesium requires the presence of guanine nucleotide triphosphates which may be essential for regulation of activity by fixing the enzyme in an active state. Quantitation of cyclic GMP (cGMP)/cAMP ratios suggests that a primary cGMP elevation occurs before a cAMP elevation (139). The formation of GTP-enzyme complexes may represent an event that occurs during the lag phase characteristic of both LT and CT.…”

“…Pretreatment with lanthanum chloride resulted in a twofold reduction in secretion due to CT and a 10fold reduction after LT exposure. This effect is postulated to be due to the inhibition of a protein kinase system, resulting in a rise in cGMP (139) and subsequent cAMP elevation after adenylate cyclase activation (139,144). DeLorenzo et al…”