Phorbol ester enhances choline uptake in cultured porcine brain endothelial cells

Choline uptake in cultured porcine endothelial cells isolated from cerebral microvessels was investigated. A large part of the choline that was taken up was incorporated into phospholipids within 24 h. Phorbol 12-myristate 13-acetate (PMA, 10^-7 M), a protein kinase C activator, enhanced choline uptake and acetylcholine (ACh) synthesis in endothelial cells. The PMA-induced enhancement of choline uptake was neither affected by calphostin C (10^-7 M), an inhibitor of protein kinase C, nor hemicholinium 3 (10^-5 M) treatment. These results suggest that brain endothelial cells have a choline uptake system, which is not identical to the high-affinity choline uptake system located in cholinergic neurons, and that the PMA-induced enhancement of choline uptake is independent of protein kinase C activation. Some of the choline taken up from the extracellular space is used for acetylcholine synthesis.