Kinetic analysis of hexose transport to determine the mechanism of amygdalin and prunasin absorption in the intestine

Evidence is accumulating that glucose-conjugated compounds may be carried across the gut mucosa via the epithelial sodium-dependent monosaccharide transporter SGLT1. A modification of the everted intestinal sac technique was utilized to study the transport of the cyanogenic glycoside amygdalin (D-mandelonitrile beta-D-gentiobioside) and its metabolite D-mandelontrile beta-D-glucoside (prunasin). Everted sacs of rat jejunum and ileum were bathed in isotonic oxygenated sodium chloride-potassium phosphate buffer containing 2.8 microCi D-[(3)H]-mannose and 0.187 microCi D-[(14)C]-glucose. For treatment groups, buffers contained phloridzin, galactose, amygdalin or prunasin. The rate constant (k) for the transport process was calculated. Compared with the control (n = 33), phloridzin (n = 25) significantly reduced the rate constants of both D-[(14)C]-glucose and D-[(3)H]-mannose. Substitution of sodium with choline and incremental galactose treatments similarly reduced D-[(14)C]-glucose influx, indicating that a fraction of the transport is carrier-mediated. Treatment with amygdalin did not significantly affect the rate constants of D-[(14)C]-glucose or D-[(3)H]-mannose transport. However, treatment with 1 mM prunasin (n = 16) did reduce the influx of D-[(14)C]-glucose without affecting D-[(3)H]-mannose values. This is consistent with the reports finding that glycoside absorption may be mediated by SGLT1.