Stimulation of ca2+ influx in at3-1 gonadotrophs via the camp/pka
signaling system.
Hezareh, Marjan, Werner Schlegel, and Stephen R. Rawlings.
Fondation Pour Recherches M[theta]dicales, University of Geneva,
CH-1211 Geneva 4, Switzerland, Departments of Pathology & Medicine
0679, University of California at San Diego, La Jolla, CA 92093,
U.S.A.
APStracts 4:0160E, 1997.
To investigate the regulation of [Ca2+]i by the cAMP signaling system
in clonal gonadotrophs, microfluorimetric recordings were made in
single, indo-1-loaded, aT3-1 cells. Forskolin, 8-Br-cAMP, or a low
concentration (100 pM) of the hypothalamic factor pituitary adenylate
cyclase-activating polypeptide (PACAP), stimulated Ca2+ step
responses or repetitive Ca2+ transients, which were blocked by the
removal of extracellular Ca2+, by the dihydropyridine (DHP) (+)PN
200-110, or by preincubation with the protein kinase A (PKA)
antagonist H-89 (10 mM). Thus activation of the cAMP/PKA system in
aT3-1 gonadotrophs stimulates Ca2+ influx through DHP-sensitive (L
-type) Ca2+ channels. In contrast, high PACAP concentrations (100 nM)
stimulated biphasic Ca2+ spike-plateau responses. The Ca2+ spike was
independent of extracellular Ca2+, and similar responses were
observed by microperfusion of individual cells with Ins(1,4,5)P3,
suggesting the involvement of the PLC signaling pathway. The Ca2+
plateau depended upon Ca2+ influx, was blocked by (+)PN 200-110, but
was only partially blocked by H-89 pretreatment. In conclusion, PACAP
stimulates [Ca2+]i increases in aT3-1 gonadotrophs through both the
PLC and AC signaling pathways. Furthermore, this is the first clear
demonstration that the cAMP/PKA system can mediate changes in [Ca2+]i
in gonadotroph-like cells.
Received 8 April 1997; accepted in final form 21 July 1997.
APS Manuscript Number E157-7.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 27 August 1997