Facilitation of glutamate release by ionotropic glutamate receptors in osteoblasts

• Published in: Biochemical and biophysical research communications Vol. 297; no. 3; pp. 452 - 458
• Main Authors: Hinoi, Eiichi, Fujimori, Sayumi, Takarada, Takeshi, Taniura, Hideo, Yoneda, Yukio
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 27.09.2002
• Subjects: alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid - metabolism; alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid - pharmacology; AMPA receptors; Animals; Animals, Newborn; BNPI; Cell Division - drug effects; Cells, Cultured; Exocytosis; Glutamate; Glutamic Acid - metabolism; Kainic Acid - pharmacology; N-Methylaspartate - pharmacology; Osteoblasts; Osteoblasts - cytology; Osteoblasts - metabolism; Potassium Chloride - pharmacology; Quinoxalines - pharmacology; Rats; Rats, Wistar; Receptors, AMPA - drug effects; Receptors, AMPA - genetics; Receptors, AMPA - metabolism; Release; Reverse Transcriptase Polymerase Chain Reaction; Skull - cytology; Vesicular transporter; BNPI; AMPA receptors; Glutamate; Vesicular transporter; Exocytosis; Osteoblasts; Release
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/S0006-291X(02)02223-4

Constitutive expression of mRNA was seen for the vesicular glutamate transporter brain-specific Na +-dependent inorganic phosphate cotransporter (BNPI), but not differentiation-associated Na +-dependent inorganic phosphate cotransporter, in rat calvarial osteoblasts cultured for 7 and 21 days in vitro (DIV). Three different agonists for ionotropic glutamate receptors (iGluR) at 1 mM, as well as 50 mM KCl, significantly increased the release of endogenous l-glutamate from osteoblasts cultured for 7 DIV when determined 5 min after the addition by using a high performance liquid chromatograph. The inhibitor of desensitization of dl-α-amino-3-hydroxy-5-methylisoxasole-4-propionate (AMPA) receptors cyclothiazide significantly potentiated and prolonged the release of endogenous l-glutamate evoked by AMPA in a dose-dependent manner. The release evoked by AMPA was significantly prevented by the addition of an AMPA receptor antagonist as well as by the removal of Ca 2+ ions. These results suggest that endogenous l-glutamate could be released from intracellular vesicular constituents associated with BNPI through activation of particular iGluR subtypes expressed in cultured rat calvarial osteoblasts.