Stimulation of Ca2+ influx in alpha T3-1 gonadotrophs via the cAMP/PKA signaling system.
To investigate the regulation of free cytosolic calcium concentration ([Ca2+]i) by the adenosine 3',5'-cyclic monophosphate (cAMP) signaling system in clonal gonadotrophs, microfluorimetric recordings were made in single indo 1-loaded alpha T3-1 cells. Forskolin, 8-bromoadenosine 3',5'-cyclic monophosphate, 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 microM). Thus activation of the cAMP/PKA system in alpha T3-1 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 D-myo-inositol 1,4,5-trisphosphate, suggesting the involvement of the phospholipase C (PLC) signaling pathway. The Ca2+ plateau depended on 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 alpha T3-1 gonadotrophs through both the PLC and adenylate cyclase signaling pathways. Furthermore, this is the first clear demonstration that the cAMP/PKA system can mediate changes in [Ca2+]i in gonadotroph-like cells.
Hezareh
M
M
Fondation pour Recherches Médicales, University of Geneva, Switzerland.
Schlegel
W
W
Rawlings
S R
SR
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology; D020746:Calcium Channels, L-Type; D002999:Clone Cells; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D007700:Kinetics; D009479:Neuropeptides / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000494:pharmacology; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D010903:Pituitary Gland, Anterior / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013449:Sulfonamides; D013997:Time Factors; D010738:Type C Phospholipases / Q000378:metabolism; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology
D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D004791:Enzyme Inhibitors; D007546:Isoquinolines; D009479:Neuropeptides; D018377:Neurotransmitter Agents; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D013449:Sulfonamides; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D014660:Vasoactive Intestinal Peptide; D015544:Inositol 1,4,5-Trisphosphate; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D010738:Type C Phospholipases; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D002118:Calcium