title: C-type natriuretic peptide (CNP) effects on intracellular calcium [Ca2+]i in mouse gonadotrope-derived alphaT3-1 cell line.
abstract: C-type natriuretic peptide (CNP), the third member of the atrial natriuretic peptide family, acts via guanylyl cyclase containing GC-B receptors to stimulate cyclic guanosine 3',5' monophosphate (cGMP) accumulation in the gonadotrope-derived alphaT3-1 cell line and rat pituitary cells. This effect is inhibited by concomitant activation of the phospholipase C (PLC)-coupled gonadotrophin hormone-releasing hormone (GnRH) receptors in these cells. Since GnRH stimulates gonadotrophin secretion from gonadotropes by increasing the cytosolic Ca2+ concentration ([Ca2+]i) and natriuretic peptides have been found to influence PLC/Ca2+ signalling in other systems, we have investigated whether CNP can alter basal or GnRH-stimulated changes in [Ca2+]i in alphaT3-1 cells. In Ca 2+-containing medium, 10(-7) M CNP modestly, but significantly increased [Ca2+]i over several min, but subsequently inhibited the elevation of [Ca2+]i in response to 10(-7) M GnRH in both Ca2+-containing and Ca2+-free medium. This inhibitory effect was mimicked by 10(-6) M 8-Br-cGMP, but not by ANP, indicating mediation by cyclic GMP and the CNP-specific GC-B receptor. However, basal and GnRH-stimulated inositol (1,4,5) trisphosphate (Ins(1,4,5)P3) generation were not measurably affected by CNP, and CNP failed to affect thapsigargin-induced capacitative Ca2+ entry. Thus, it appears that the cross-talk between CNP and GnRH in these cells is reciprocal in that GnRH modulates CNP effects on cGMP generation, whereas, CNP modulates GnRH effects on Ca2+ mobilisation.
authors.affiliation: University of Bristol, Division of Medicine, Department of Hospital Medicine, UK. r.c.fowkes@mds.qmw.ac.uk
authors.forename: R C
authors.initials: RC
authors.lastname: Fowkes
authors.forename: W
authors.initials: W
authors.lastname: Forrest-Owen
authors.forename: B
authors.initials: B
authors.lastname: Williams
authors.forename: C A
authors.initials: CA
authors.lastname: McArdle
mesh_terms: D000818:Animals; D009320:Atrial Natriuretic Factor / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D051379:Mice; D020098:Natriuretic Peptide, C-Type / Q000494:pharmacology*; D010902:Pituitary Gland / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism
chemical_list: D020098:Natriuretic Peptide, C-Type; C016276:8-bromocyclic GMP; D015544:Inositol 1,4,5-Trisphosphate; D009320:Atrial Natriuretic Factor; D006152:Cyclic GMP; D002118:Calcium