Journal of Neuroscience, Vol 12, 1077-1085, Copyright © 1992 by Society for Neuroscience
Pharmacological characterization of endothelin-stimulated phosphoinositide breakdown and cytosolic free Ca2+ rise in rat C6 glioma cells
WW Lin, JG Kiang and DM Chuang
Biological Psychiatry Branch, National Institute of Mental Health, Bethesda, Maryland 20892.
Because increasing evidence indicates that glial cells are a target of
endothelin, we have characterized endothelin-induced phosphoinositide (PI)
turnover and Ca2+ homeostasis in C6 glioma cells. Endothelin-1 (ET)
increased formation of 3H-inositol phosphate (IP) from PI and elicited an
increase in cytosolic free Ca2+ ([Ca2+]i) in rat C6 glioma. In the presence
of Li+, the increase in 3H-inositol trisphosphate formation was rapid,
reaching its peak at 5 min after stimulation. ET also elicited a rapid and
sustained increase in [Ca2+]i in a dose- dependent manner (1-100 nM). The
rank orders of efficacy for ET-related peptides in increasing [Ca2+]i were
ET = ET-2 greater than sarafotoxin greater than ET-3. Both ET-mediated
stimulation of IP formation and [Ca2+]i increase were largely inhibited in
the absence of external Ca2+ but unaffected by the depletion of external
Na+ and the presence of dihydropyridine derivatives or verapamil. Inorganic
Ca2+ channel blockers Cd2+, La3+, and Mn2+ at 1 mM inhibited both responses
induced by ET. Cross-desensitization and nonadditivity were observed for
both events among ET-related peptides tested, but not between ET and ATP.
Pretreatment of cells with pertussis toxin (PTX) attenuated the PI response
to ET, but had no effect on ET-elicited [Ca2+]i increase. ET- induced Ca2+
mobilization (measured in Ca(2+)-free medium) was only transient and was
inhibited by 8-(N,N-diethylamino)octyl-3,4,5- trimethoxybenzoate. Moreover,
the intracellular Ca2+ pools mobilized by ET and ATP appeared to overlap,
as indicated by their partial heterologous desensitization.(ABSTRACT
TRUNCATED AT 250 WORDS)