Purpose. We examined the functional properties of choline transport across the blood-brain barrier (BBB) in mice. We compared the kinetic parameters and transport properties with those found in our in vitro uptake experiments using mouse brain capillary endothelial cells (MBEC4). Methods. The permeability coefficient-surface area product (PS) values of [3H]choline at the BBB were estimated by means of an in situ brain perfusion technique in mice. Results. [3H]Choline uptake was well described by a two-component model: a saturable component and a nonsaturable linear component. The [3H]choline uptake was independent of pH and Na+, but was significantly decreased by the replacement of Na+ with K+. Various basic drugs, including substrates and inhibitors of the organic cation transporter, significantly inhibited the [3H]choline uptake. These in situ (in vivo) results corresponded well to the in vitro results and suggest that the choline transporter at the BBB is a member of the organic cation transporter (OCT) family. Conclusion. The choline transport mechanism at the BBB is retained in MBEC4.
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