Rapid modulatory effect of estradiol on acetylcholine-induced Ca2+ signal is mediated through cyclic-GMP cascade in LHRH-releasing GT1-7 cells.
Hypothalamic luteinizing hormone-releasing hormone neurons (LHRH) form the final pathway for the central control of reproduction through the release of LHRH into the pituitary-hypothalamic system. We previously found that LHRH-producing GT1-7 cells respond to acetylcholine (ACh) with an increase in intracellular calcium ([Ca2+]i) through activation of muscarinic receptors. This effect is acutely modulated by 17beta-estradiol in a manner compatible with specific membrane binding sites. Because increasing evidence suggests that second messengers are involved in the rapid action of estradiol, the aim of the present study was to identify the pathway underlying estrogen actions on ACh-induced Ca2+ signals. 8-Bromoguanosine 3',5'-cyclic monophosphate (10 microm) and C-type natriuretic peptide (10 microm) mimicked the effect of estradiol. On the contrary, neither dibutyryl cAMP (100 microm), forskolin (100 nm or 10 microm), or sodium nitroprusside (10 microm) induced any modification of [Ca2+]i in response to ACh. The effect of estradiol on calcium transients was totally blocked by two different cGMP-dependent protein kinase (PKG) inhibitors. In addition, phosphorylation of inositol 1,4,5-triphosphate (IP3) receptor was rapidly induced by estradiol but totally blocked when the cells were pretreated with a PKG inhibitor. We conclude that physiological concentrations of estradiol reduce ACh-induced Ca2+ transients via a mechanism involving a membrane-associated guanylate cyclase, which finally induces a PKG-dependent IP3 receptor phosphorylation that modifies calcium release from the endoplasmic reticulum.
Morales
Araceli
A
Department of Physiology, Institute of Biomedical Technologies, University of La Laguna, La Laguna, 38071 Santa Cruz de Tenerife, Spain.
Díaz
Mario
M
Guelmes
Pedro
P
Marín
Raquel
R
Alonso
Rafael
R
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D001345:Autoradiography / Q000379:methods; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D017869:Cyclic GMP-Dependent Protein Kinases / Q000502:physiology; D004347:Drug Interactions; D004958:Estradiol / Q000494:pharmacology*; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D053496:Inositol 1,4,5-Trisphosphate Receptors; D051379:Mice; D008954:Models, Biological; D045265:Natriuretic Peptides / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism
D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D045265:Natriuretic Peptides; D020030:Nitric Oxide Donors; D018160:Receptors, Cytoplasmic and Nuclear; D009599:Nitroprusside; D005576:Colforsin; C016276:8-bromocyclic GMP; D007987:Gonadotropin-Releasing Hormone; D004958:Estradiol; D017869:Cyclic GMP-Dependent Protein Kinases; D006152:Cyclic GMP; D000109:Acetylcholine; D002118:Calcium