Effect of exogenous ATP on Momordica charantia Linn. (Cucurbitaceae) induced inhibition of D-glucose, L-tyrosine and fluid transport across rat everted intestinal sacs in vitro

Momordica charantia (MC) is a common oriental vegetable with known antidiabetic, laxative and antimicrobial properties. This study investigates the effects of aqueous fruit extract of MC on the transport of D-glucose, L-tyrosine and fluid across rat-everted intestine in vitro. Everted intestinal sacs from rats were mounted in an organ bath containing Krebs-Henseleit bicarbonate buffer. Graded concentrations (1.5-12 mg/ml) of MC fruit extract were incubated in the mucosal solution with and without exogenous ATP in the mucosal bathing fluid. The serosal appearance and mucosal disappearance Of D-glucose, L-tyrosine and the fluid absorptive capacity of the intestine were significantly inhibited (P < 0.05) with increasing graded concentrations of MC. The concentration Of D-glucose accumulated or metabolized by the enterocytes in the intestinal tissues were significantly higher (p < 0.05) when incubated with MC. Increasing graded concentrations of exogenous ATP (25-200 mu M) were incubated with 3.0 mg/ml MC to confirm inhibition of the ATP-dependent active transport of D-glucose, L-tyrosine and fluid across rat enterocytes. It was found that increasing concentrations of mucosal ATP from 25 to 100 mu M significantly (P < 0.05) reverses the MC-depression of the D-glucose, L-tyrosine and fluid uptake across rat everted intestinal sacs. It is hypothesized that bioactive phytochemicals such as saponins in MC fruit extract inhibits the active transport Of D-glucose, L-tyrosine and fluid across rat intestine by inhibiting the production of ATP responsible for the active transport of these molecules. It is likely that MC can be a potential alternative drug therapy of postprandial hyperglycaemia via inhibition of glucose uptake across the small intestine. (c) 2006 Elsevier Ireland Ltd. All rights reserved.