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Endothelin downregulates the glutamate transporter GLAST in cAMP‐differentiated astrocytes in vitro
Author(s) -
Matsuura Sigeru,
Ikegaya Yuji,
Yamada Maki K.,
Nishiyama Nobuyoshi,
Matsuki Norio
Publication year - 2002
Publication title -
glia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.954
H-Index - 164
eISSN - 1098-1136
pISSN - 0894-1491
DOI - 10.1002/glia.10020
Subject(s) - glutamate receptor , biology , astrocyte , endothelin 1 , adenosine , endocrinology , glutamate aspartate transporter , medicine , transporter , receptor , microbiology and biotechnology , excitatory amino acid transporter , central nervous system , biochemistry , gene
Abstract Endothelin (ET) is a putative pathogenetic mediator associated with brain trauma and ischemia. Because a link between neuronal damage after these injuries and glial Na + ‐dependent L‐ glutamate transporter activity has been suggested, we investigated the effect of ET on the glutamate clearance ability of astrocytes. Dibutyryl cyclic adenosine monophosphate (dBcAMP), which is widely used to induce differentiation of cultured astrocytes, markedly increased [ 3 H]glutamate transport activity in a concentration‐ and time‐dependent manner. In the presence of ET, however, dBcAMP decreased the glutamate uptake. This effect was efficiently prevented by an antagonist of ET B receptor, but not of ET A receptor. ET per se was virtually ineffective. Eadie–Hofstee analysis demonstrated that dBcAMP increased the V max value of glutamate uptake activity by 43.4% in the absence of ET, but decreased it by 41.4% in the presence of ET, without apparent changes in the K m value. Accordingly, Western blot analysis indicated that the change in transport activity correlated closely with that in expression level of the glial glutamate transporter GLAST. These results may represent the mechanisms by which ET aggravates trauma‐ and ischemia‐elicited neuronal damage. GLIA 37:178–182, 2002. © 2002 Wiley‐Liss, Inc.