Transepithelial dipeptide (glycylsarcosine) transport across epithelial monolayers of human Caco-2 cells is rheogenic
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Net transepithelial transport (and cellular accumulation) of the dipeptide glycylsarcosine (Gly-Sar), across the apical membrane of human intestinal Caco-2 epithelia, is driven by a proton gradient (Na+-free conditions) and displays saturation kinetics (Km 17.4±5.1 mM, Vmax of 92.8±15.6 nmol.cm−2.h−1). Net Gly-Sar transport is associated with the stimulation of an inward short-circuit current (Isc). This dipeptide-stimulated Isc is observed in both Na+-containing and Na+-free conditions, is stimulated by apical acidity, and displays saturation kinetics (in Na+-free media at apical pH 6.0, Km of 13.6±4.5 mM and a Vmax of 284.1±39.3 nmol.cm−2.h−1). The maximal capacities of Gly-Sar transport and Isc suggest a dipeptide/proton stoichiometry greater than unity (1∶3).
Key wordsCaco-2 cells dipeptide epithelia H+ symport intestine pHi short-circuit current
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