title: High magnesium concentration inhibits ligand-stimulated calcium influx and hormone secretion in rat pituitary lactotropes with involvement of intracellular free magnesium.
abstract: The effects of extracellular magnesium concentration ([Mg2+]ex) on thyrotropin-releasing hormone (TRH)-stimulated intracellular free calcium mobilization and prolactin secretion were investigated concomitantly with measurement of the intracellular free magnesium concentration ([Mg2+]i). TRH-stimulated intracellular free calcium mobilization was significantly inhibited when the medium was replaced by high Mg2+ medium ([Mg2+]ex = 10 mM) in normal Ca2+ medium. The inhibitory effects of high Mg2+ became apparent concomitantly with an increase in [Mg2+]i from 0.7 to 1.3 mM. High Mg2+ significantly inhibited TRH-induced PRL secretion in a dose-dependent manner in normal Ca2+ medium. TRH-stimulated inositol triphosphate (IP3) production was rather augmented by the replacement with high Mg2+ medium. In summary, high Mg2+ inhibits Ca2+ influx stimulated by TRH in the rat pituitary lactotropes, possibly with the involvement of [Mg2+]i increase. These results have general importance in relation to high Mg(2+)-induced suppression of the biological functions of cells.
authors.affiliation: Department of Obstetrics and Gynecology, Osaka University Medical School, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Kasahara
authors.forename: K
authors.initials: K
authors.lastname: Tasaka
authors.forename: N
authors.initials: N
authors.lastname: Masumoto
authors.forename: T
authors.initials: T
authors.lastname: Nishizaki
authors.forename: J
authors.initials: J
authors.lastname: Mizuki
authors.forename: M
authors.initials: M
authors.lastname: Tahara
authors.forename: A
authors.initials: A
authors.lastname: Miyake
authors.forename: O
authors.initials: O
authors.lastname: Tanizawa
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005260:Female; D007295:Inositol Phosphates / Q000378:metabolism; D008274:Magnesium / Q000494:pharmacology*; D010903:Pituitary Gland, Anterior / Q000187:drug effects*; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology
chemical_list: D007295:Inositol Phosphates; D013973:Thyrotropin-Releasing Hormone; D011388:Prolactin; D008274:Magnesium; D002118:Calcium