title: Sodium-calcium exchangers in rat ameloblasts.
abstract: Although the central role of ameloblasts in synthesis and resorption of enamel matrix proteins during amelogenesis is well documented, the Ca(2+)-transport/extrusion mechanism remains to be fully elucidated. To clarify Ca(2+)-transport in rat ameloblasts, we investigated expression and localization of Na(+)-Ca(2+) exchanger (NCX) isoforms and the functional characteristics of their ion transporting/pharmacological properties. RT-PCR and immunohistochemical analyses revealed expression of NCX1 and NCX3 in ameloblasts, localized in the apical membrane. In patch-clamp recordings, Ca(2+) efflux by Na(+)-Ca(2+) exchange showed dependence on external Na(+). Ca(2+) influx by Na(+)-Ca(2+) exchange, measured by fura-2 fluorescence, showed dependence on extracellular Ca(2+) concentration, and it was blocked by NCX inhibitors KB-R7943, SEA0400, and SN-6. These results showed significant expression of NCX1 and NCX3 in ameloblasts, indicating their involvement in the directional Ca(2+) extrusion pathway from cells to the enamel mineralizing front.
authors.affiliation: Oral Health Science Center, hrc7, Tokyo Dental College, Mihama-ku, Chiba 261-8502, Japan.
authors.forename: Reijiro
authors.initials: R
authors.lastname: Okumura
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Shibukawa
authors.forename: Takashi
authors.initials: T
authors.lastname: Muramatsu
authors.forename: Sadamitsu
authors.initials: S
authors.lastname: Hashimoto
authors.forename: Kan-Ichi
authors.initials: K
authors.lastname: Nakagawa
authors.forename: Masakazu
authors.initials: M
authors.lastname: Tazaki
authors.forename: Masaki
authors.initials: M
authors.lastname: Shimono
mesh_terms: D000565:Ameloblasts / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005456:Fluorescent Dyes / Q000737:chemistry; D016257:Fura-2 / Q000737:chemistry; D015870:Gene Expression; D018408:Patch-Clamp Techniques; D020033:Protein Isoforms; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012964:Sodium / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000235:genetics / Q000378:metabolism*
chemical_list: D005456:Fluorescent Dyes; C499849:NCX1 protein, mouse; D020033:Protein Isoforms; C491101:Slc8a3 protein, mouse; D019831:Sodium-Calcium Exchanger; D012964:Sodium; D002118:Calcium; D016257:Fura-2