PHORBOL ESTER ENHANCES CHOLINE UPTAKE IN CULTURED PORCINE BRAIN ENDOTHELIAL-CELLS

Choline uptake in cultured porcine endothelial cells isolated from cer ebral 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 endothel ial cells. The PMA-induced enhancement of choline uptake was neither a ffected by calphostin C (10(-7) M), an inhibitor of protein kinase C, nor hemicholinium 3 (10(-5) M) treatment. These results suggest that b rain endothelial cells have a choline uptake system, which is not iden tical to the high-affinity choline uptake system located in cholinergi c neurons, and that the PMA-induced enhancement of choline uptake is i ndependent of protein kinase C activation. Some of the choline taken u p from the extracellular space is used for acetylcholine synthesis.