Thiamine transport by basolateral rat liver plasma membrane vesicles

摘要: Hepatic thiamine transport is thought to be a saturable, Na(+)- and energy-dependent process. However, the of this organic cation has not been examined in experimental models that allow direct characterization carrier-mediated processes. Recently, sinusoidal cation/H+ antiport was identified, using N1-methylnicotinamide as marker. To determine whether substrate for antiport, characteristics uptake were rat liver basolateral membrane vesicles. An inwardly directed Na+ gradient had no effect on compared with an identical K+ gradient. outwardly H+ stimulated pH-equilibrated conditions, H(+)-dependent result diffusion potential. Identical pH gradients under voltage-clamped consistent electroneutral thiamine/H+ exchange. Unlabeled intravesicular trans-stimulated [3H]thiamine uptake. Choline imipramine cis-inhibited exchange; series other cations analogues effect. Carrier-mediated showed two saturable systems. In conclusion, present membrane, distinct from Na+/H+ NMN+/H+