Influence of peppermint oil on absorptive and secretory processes in rat small intestine

Background-Peppermint oil is used to relieve the symptoms of irritable bowel syndrome, relaxing intestinal smooth muscle by reducing the availability of calcium, but its effects on intestinal transport are unknown. Aims-To determine the effect of peppermint oil on intestinal transport processes. Methods-The influence of peppermint oil on intestinal transport was investigated in rat jejunum using both intestinal sheets mounted in Ussing chambers and brush border membrane vesicles. Results-Mucosal peppermint oil (1 and 5 mg/ml) had no significant effect on basal short circuit current, but inhibited the increase associated with sodium dependent glucose absorption. The increased short circuit current induced by serosal acetylcholine, a reflection of calcium mediated electrogenic chloride secretion, was unaffected by mucosal peppermint oil (5 mg/ml). In contrast, serosal peppermint oil (1 mg/ml) inhibited the response to acetylcholine without reducing the effect of mucosal glucose. In brush border membrane vesicles active glucose uptake was inhibited by extravesicular peppermint oil at concentrations of 0.5 and 1 mg/ml. Conclusions-Peppermint oil in the intestinal lumen inhibits enterocyte glucose uptake via a direct action at the brush border membrane. Inhibition of secretion by serosal peppermint oil is consistent with a reduced availability of calcium.