Endothelin-1 (ET-1) is a potent vasoconstrictor peptide that is also known
to induce a wide spectrum of biological responses in nonvascular tissue. In
this study, we found that ET-1 (100 nM) inhibited the glutamate uptake in
cultured astrocytes expressing the glutamate/aspartate transporter (GLAST);
astrocytes did not express the glutamate transporter-1 (GLT-1). The V-max
and the K-m of the glutamate uptake were reduced by 57% and 47%, respective
ly. Application of the ETA and ETB receptor antagonists BQ-123 and BQ-788 p
artly inhibited the ET-1-evoked decrease in the glutamate uptake, whereas t
he nonspecific ET receptor antagonist bosentan completely inhibited this de
crease. Incubation of the cultures with pertussis toxin abolished the effec
t of ET-1 on the uptake. The ET-1-induced decrease in the glutamate uptake
was independent of extracellular free Ca2+ concentration, whereas the intra
cellular Ca2+ antagonists thapsigargin and 3,4,5-trimethoxybenzoic acid 8-(
diethylamino) octyl ester abolished the effect of ET-1 on the glutamate upt
ake. Incubation with the protein kinase C (PKC) antagonist staurosporine, b
ut not with the fatty acid-binding protein bovine serum albumin, prevented
the ET-1-induced decrease in the glutamate uptake. These results suggest th
at ET-1 impairs the high-affinity glutamate uptake in cultured astrocytes t
hrough a G protein-coupled mechanism, involving PKC and changes in intracel
lular Ca2+.