Regulation of taurine transport in rat astrocytes by protein kinase c: role of calcium and calmodulin. C., Tchoumkeu-Nzouessa Guizot, and Rebel G[acute]erard. Institut de Recherche Contre les Cancers de l'Appareil Digestif (IRCAD) - H[circumflex]opitaux Universitaires. BP 426. F 67091 STRASBOURG-FRANCE
APStracts 2:0373C, 1995.
Phorbol 12-myristate 13-acetate, a potent stimulator of PKC, inhibited taurine uptake in rat astrocytes. This effect was mimicked by oleoyl acetyl glycerol an endogenous stimulator of PKC and by R59949, an inhibitor of diacyl glycerol kinase. Maximal inhibition was obtained at 1[mu]M PMA after 1 hour of treatment. This effect was prevented by pretreatment of the cells with chelerythrine, a potent and selective inhibitor of PKC. The transport of [beta]-alanine, an amino acid that shares the same transporter as taurine, was inhibited at a comparable extent. The effect of PMA was potentiated by co-treatment of the cells with thapsigargin or calcium ionophore A23187. However, EGTA and verapamil did not prevent the PMA effect. Pretreatment of the cells with calmodulin antagonists W-13 or R24571, prevent the PMA -induced inhibition of taurine uptake. This inhibition was not affected by cycloheximide, actinomycin D, colchicine or cytochalasin D. The Na+:Cl-:taurine coupling ratio were unaffected. Dimethyl -amiloride, a selective inhibitor of Na+-H+ antiport was unable to prevent the effects of PMA. These effects were associated with a decrease in the maximal velocity and an increase in the Michaelis -Menten constant. 

Received 26 May 1995; accepted in final form 26 September 1995.
APS Manuscript Number C306-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95