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Effect of endothelin‐1 on astrocytic protein content
Author(s) -
Hasselblatt Martin,
Bunte Marion,
Dringen Ralf,
Tabernero Arantxa,
Medina José M.,
Giaume Christian,
Sirén AnnaLeena,
Ehrenreich Hannelore
Publication year - 2003
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.10224
Subject(s) - cycloheximide , biology , astrocyte , gap junction , tolbutamide , carbenoxolone , receptor , neuroglia , channel blocker , protein synthesis inhibitor , endocrinology , medicine , endothelin 1 , microbiology and biotechnology , protein biosynthesis , calcium , biochemistry , intracellular , diabetes mellitus , central nervous system
The astrocytic endothelin (ET) receptors, ET A and ET B , modulate calcium signaling and the astrocytic gap junctional network. The nonselective ET receptor ligand ET‐1 inhibits gap junction permeability, an effect that can be blocked by tolbutamide. This mechanism may play a role in pathophysiological conditions such as ischemic stroke, characterized by elevated tissue ET‐1 levels and hypertrophic‐appearing reactive astrocytes. Therefore, the effect of ET‐1 on cellular protein content was investigated in confluent once‐passaged rat astrocyte cultures under serum‐free conditions, by the Lowry method. Gap junction permeability was determined by the dye transfer technique. ET‐1 prevented the decrease in astrocytic protein content observed in controls. The effect of ET‐1 on cellular protein content was most pronounced in cultures seeded at high density, but it was attenuated in ET B ‐deficient (sl/sl) astrocytes. This effect could be blocked by the nonselective ET antagonist LU 302872 (10 μM), as well as by the protein synthesis inhibitor cycloheximide (10 μM). This increase in astrocytic protein content was inhibited by the ATP‐sensitive K + channel blocker tolbutamide, which also antagonized the ET‐1‐induced reduction of gap junction permeability and reversed the morphological changes observed in astrocytes upon ET‐1 treatment. Cytosine arabinoside (10 μM), a DNA synthesis blocker, inhibited the ET‐1‐induced BrdU uptake without affecting the ET‐1‐induced increase in astrocytic protein content. To conclude, ET‐1 induces an increase in astrocytic protein content as well as changes in astrocyte morphology in vitro. This hypertrophic response involves uncoupling of the astrocytic gap junctional network and is not dependent on DNA synthesis. GLIA 42:390–397, 2003. © 2003 Wiley‐Liss, Inc.