Characterization of the transport of the organic cation [ 3 H]MPP + in human intestinal epithelial (Caco-2) cells

Abstract

The aim of this study was to characterize the transport of organic cations at the intestinal level, by studying the characteristics of the transport of 1-methyl-4-phenylpyridinium (MPP+) in Caco-2 cells. Transepithelial flux as well as cellular accumulation of [3H]MPP+ were quantitatively similar when substrate was applied from the basolateral or apical cell membrane. Verapamil (100 microM) and rhodamine123 (10 microM) significantly reduced [3H]MPP+ transepithelial flux in the apical-to-basolateral direction. When cells were grown on plastic supports, [3H]MPP+ was rapidly accumulated in the cells, both by saturable and nonsaturable mechanisms. The kinetic parameters of the saturable component were: Km: 449 microM and Vmax: 2,249 pmol per mg protein and 5 min. Uptake of [3H]MPP+ was metabolic energy-dependent and Na+-, pH- and potential-independent. It was inhibited by several organic cations (verapamil, rhodamine123, daunomycin, vinblastine, tetrabutylammonium and vecuronium) but not by others (tetraethylammonium and N-methylnicotinamide). Decynium22 and corticosterone inhibited [3H]MPP+ uptake into the cells. The P-glycoprotein antibody UIC2 (20 microg/ml) had no effect. In conclusion, [3H]MPP+ is efficiently transported by Caco-2 cells in both basolateral-to-apical (secretion) and apical-to-basolateral (absorption) directions. Absorption of [3H]MPP+ at the apical membrane seems to occur through a carrier-mediated mechanism belonging to the Amphiphilic Solute Facilitator (ASF) family of transporters, but distinct from the known members of this family.

Calcium-Selective Ion Channel, CaT1, Is Apically Localized in Gastrointestinal Tract Epithelia and Is Aberrantly Expressed in Human Malignancies

“…Localization of the CaT1 protein on the brush border apical surface of intestinal villi in duodenum, small intestine, and colon is consistent with CaT1's proposed role as a major transcellular mediator of Ca 2ϩ transport out of the intestinal lumen. Other ion channels and transporters have been found to localize to the apical surface of enterocytes in a similar pattern to the one we have observed for CaT1 (Geibel et al, 2000;Marshall et al, 2002;Martel et al, 2000;Murer et al, 2001;Sangan et al, 2002).…”

Modulation of MPP+ uptake by procyanidins in Caco‐2 cells: Involvement of oxidation/reduction reactions

“…The effect of these fractions on the modulation of intestinal uptake of 3 H-MPP + was studied. As previously shown by Martel et al [20] The organic cation uptake by Caco-2 cells was more pronounced when structurally more complex procyanidins were tested, fraction V presenting the highest uptake (262.2 ± 7.44% of control). The results also suggest that cell exposure time to these compounds may influence their effect.…”

The Calcium Channel CaT1 in Prostate Cancer Progression

“…Localization of the CaTl protein on the brush border apical surface of Intestinal villi in duodenum, small Intestine, and colon Is consistent with CaTI's proposed role as a major transcellular mediator of Ca^"^ transport out of the intestinal lumen. Other Ion channels and transporters have been found to localize to the apical surface of enterocytes in a similar pattern to the one we have observed for CaTl (Gelbel et al, 2000;Marshall et al, 2002;Martel et al, 2000;Murer et al, 2001;Sangan et al, 2002).…”