Eta and etb receptors cooperate in dna synthesis via opposing
regulations of camp in human lung cell line.
Takimoto, Misato, Kyoko Oda, Thomas Fr_h, Michihiro Takai, Toshikazu
Okada, and Yukio Sasaki.
International Research Laboratories, Ciba-Geigy Japan Ltd.,
Takarazuka 665, Japan
APStracts 3:0062L, 1996.
We investigated the contribution of ETA and ETB receptors on
endothelin (ET)-induced DNA synthesis in CCD-18Lu cells, a human lung
cell line possessing both ETA and ETB (ETA/ETB ratio: 9/1). ET-1
(0.05-2 nM) potently induced [3H]thymidine incorporation by 2-14
folds over the basal level. An ETA selective antagonist, FR139317,
inhibited 0.2 nM ET-1-induced DNA synthesis dose-dependently, showing
complete inhibition at 1 [mu]M. ET-3 was inactive up to 2 nM. In
contrast, ETB selective antagonists, 100 nM of BQ-788 or IRL 2500,
partially (30-60%) inhibited 0.2 nM ET-1-induced DNA synthesis.
Stimulation of either ETA or ETB evoked the increases in
intracellular Ca2+ concentration ([Ca2+]i). ETB-mediated, but not ET
-1-induced, [Ca2+]i increase was pertussis toxin (PTX)-sensitive.
Cyclic AMP formation via ETA was observed in PTX-treated cells,
whereas the inhibition of isoproterenol-stimulated cAMP formation via
ETB was observed in PTX-untreated cells. Like the ETB selective
antagonists, PTX treatment or dibutyryl cAMP partially (5070%)
inhibited ET-1-induced DNA synthesis. These data suggest that 1) ET-1
induces DNA synthesis predominantly through ETA, via PTX-insensitive
G protein; 2) ETA-mediated cAMP formation inhibits DNA synthesis; and
3) stimulation of ETB coupling to Gi protein modulates ETA-mediated
DNA synthesis by inhibiting cAMP formation.
Received 16 January 1996; accepted in final form 16 April 1996.
APS Manuscript Number L11-6.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 8 May 96