Na+/Ca2+ exchanger isoforms of rat odontoblasts and osteoblasts.
In odontoblasts as well as osteoblasts, a number of mechanisms for the inflow and extrusion of Ca2+ have been demonstrated. The entrance of Ca2+ ions into odontoblasts occurs mainly through voltage-gated calcium channels. Extrusion of Ca2+ is found to be an ATP-dependent process and, in addition, Na+/Ca2+-antiports exist, which are provoked by extracellular Na+. The aim of this study was to identify the Na+/Ca2+-antiport isoforms expressed in dentinogenically active rat incisor odontoblasts and to make a comparison with different osteoblastic cells. Using RT-PCR and RNAse protection assay, we demonstrated the expression of three different isoforms, NaCa 3, 7, and 10, of the NCX1-encoded antiport in odontoblasts and osteoblastic cells. When incubated in the presence of Na+, dissected rat incisor odontoblasts as well as the osteoblastic cells extruded Ca2+ ions, as detected by chlorotetracycline and Fura-2 fluorometry, thus supporting a physiological role for the detected isoform expression. Odontoblasts and rat calvarial osteoblasts, as well as osteoblast-like cell lines UMR-106.01 and Saos-2, were shown to exhibit identical phenotypes of Na+/Ca2+-antiport isoform expression, different from the expression patterns of other tissues. The significance of this specific expression pattern is unknown, but there is a possibility that it is in some way related to the unique demands on these cell types to produce mineralized connective tissue.
Lundquist
P
P
Department of Oral Biochemistry, Göteborg University, Sweden.
Lundgren
T
T
Gritli-Linde
A
A
Linde
A
A
D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D002118:Calcium / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015870:Gene Expression; D006801:Humans; D008297:Male; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D009804:Odontoblasts / Q000378:metabolism*; D010006:Osteoblasts / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012260:Ribonucleases; D017386:Sequence Homology, Amino Acid; D012964:Sodium / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000235:genetics* / Q000378:metabolism; D014407:Tumor Cells, Cultured
D026901:Membrane Transport Proteins; C415763:NCX10 protein, rat; D020033:Protein Isoforms; C101832:SLC38A3 protein, human; C491102:Slc8a3 protein, rat; D019831:Sodium-Calcium Exchanger; D012964:Sodium; D012260:Ribonucleases; D002118:Calcium