Aim: 

To investigate the effect of high glucose exposure on the absorption of folate (FA) by Caco-2 cells.

Results: 

Apical high glucose did not affect the apical uptake of ³H-FA. Both different concentrations of glucose (10-45 mM) and different exposure times (10 min – 24 h) were tested. Also, apical high glucose (30 mM) did not affect the intracellular steady-state levels of ³H-FA, and simultaneous apical and basolateral high glucose (30 mM) did not change the apical-to-basolateral apparent permeability (P) to ³H-FA. Both the apical uptake and the steady-state intracellular levels of ^app3H-FA were strongly reduced by 5-methyltetrahydrofolate, methotrexate, SITS, DIDS and indomethacin, but were almost not affected by p – aminohippuric acid and fumitremorgin C. Moreover, DIDS and indomethacin significantly reduced (by 50-60%) the apical-to-basolateral P_app to ³H-FA, but ³H-FA present in the cells at the end of the experiment was higher in the case of indomethacin. Fumitremorgin C had no effect. The effect of the drugs was not changed or only hardly changed by high glucose.

Conclusions: 

Absorption of ³H-FA is not modulated by either apical or basolateral high glucose exposure in Caco-2 cells. Moreover, the apical uptake of ³H-FA by Caco-2 cells seems to involve RFC (but not OAT), and MRP and/or OAT (but not BCRP) may mediate apical efflux of ³H-FA.

Supported by FCT (POCI/ SAU – FCF/ 59382/ 2004)