ACTIVATION OF PROTEIN-KINASE-C DOWN-REGULATES GLIAL BUT NOT NEURONAL TAURINE UPTAKE

Phorbol myristate acetate (PMA), a protein kinase C (PKC) activator si gnificantly decreased in a time- and dose-dependent manner taurine upt ake by rat astroglial but not neuronal cells. The PMA-induced inhibiti on of taurine uptake by rat astrocytes was prevented by chelerythrine, a potent and selective inhibitor of PKC. The differential effect of P MA on rat neuronal and astroglial taurine transport was also obtained with the protein phosphatase inhibitor okadaic acid. This was not only the feature of rat cells since the same differential effects were obt ained with human glioma GL15 and human neuroblastoma IMR32 cell lines. The results suggest that the neuronal and astroglial taurine transpor ter may be structurally different.