Showing papers by "Masato Inazu published in 2005"
TL;DR: It is concluded that rat astrocytes express an intermediate‐affinity Na+‐independent choline transport system that seems to occur through a CTL1 and is responsible for the uptake of choline and organic cations in these cells.
Abstract: In this study, we examined the molecular and functional characterization of choline uptake into cultured rat cortical astrocytes. Choline uptake into astrocytes showed little dependence on extracellular Na + .N a + -independent choline uptake was saturable and mediated by a single transport system, with an apparent Michaelis–Menten constant (Km) of 35.7 ± 4.1 lM and a maximal velocity (Vmax) of 49.1 ± 2.0 pmol/mg protein/ min. Choline uptake was significantly decreased by acidification of the extracellular medium and by membrane depolarization. Na + -independent choline uptake was inhibited by unlabeled choline, acetylcholine and the choline analogue hemicholinium-3. The prototypical organic cation tetrahexylammonium (TEA), and other n-tetraalkylammonium compounds such as tetrabutylammonium (TBA) and tetrahexylammonium (THA), inhibited Na + -independent choline uptake, and their inhibitory potencies were in the order THA > TBA > TEA. Various organic cations, such as 1-methyl-4-tetrahydropyridinium (MPP + ), clonidine, quinine,
81 citations