Endothelins modulate dibutyryl cAMP-induced stellation of cultured astrocytes.
Effect of endothelin-3 (ET-3) on dibutyryl cAMP (DBcAMP)-induced stellation of rat cerebral cultured astrocytes was examined. Treatment with 1 mM DBcAMP, 10 microM forskolin, 100 microM isoproterenol and 500 nM phorbol 12-myristate 13-acetate changed protoplasmic cultured astrocytes into process-bearing ones. ET-3 (1 nM) completely prevented the astrocytic stellation induced by these agents. The effect of ET-3 showed a dose-dependence, where IC50 value and maximal effective dose were 49 pM and about 0.1 nM, respectively. ET-1 and sarafotoxin (SRTX) S6b prevented the DBcAMP-induced astrocytic stellation with potencies similar to that of ET-3. ET-3 (1 nM) did not affect the cAMP accumulation after DBcAMP treatment in cultured astrocytes. Stellate astrocytes were reversed to the protoplasmic type cells by addition of 1 nM ET-3 in the presence of DBcAMP. ET-1 and SRTX similarly reversed the astrocytic stellation. ET-3 reversed the astrocytic stellation in the absence of extracellular Ca2+. Pre-loading of BAPTA-AM, a permeable Ca2+ chelator, on stellate astrocytes had no effect on the reversal by ET-3. ET-3 did not increase intracellular free Ca2+ concentration ([Ca2+]i) of most astrocytes tested at 0.1 nM. A high concentration (100 nM) of ET-3 increased astrocytic [Ca2+]i which was negated by Ca(2+)-free and BAPTA-AM loading. These results suggest that ETs modulate morphological changes in astrocytes through cAMP- and Ca(2+)-independent mechanisms.
Department of Pharmacology, Faculty of Pharmaceutical Sciences, Osaka University, Suita, Japan.
Y
Y
Koyama
T
T
Ishibashi
K
K
Hayata
A
A
Baba
D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D003994:Bucladesine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology* / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D016232:Endothelins / Q000494:pharmacology*; D007545:Isoproterenol / Q000494:pharmacology*; D007700:Kinetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors; D014757:Viper Venoms / Q000494:pharmacology
D016232:Endothelins; D014757:Viper Venoms; C057354:sarafotoxins s6; D005576:Colforsin; D004533:Egtazic Acid; D003994:Bucladesine; D000242:Cyclic AMP; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D007545:Isoproterenol; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium