Phosphate and calcium uptake by rat odontoblast-like MRPC-1 cells concomitant with mineralization.
It has been suggested that odontoblasts are instrumental in translocating Ca2+ and inorganic phosphate (Pi) ions during the mineralization of dentin. The aim of this study was to characterize cellular Pi and Ca2+ uptake in the novel rat odontoblast-like cell line mineralizing rat pulpal cell line (MRPC) 1 during mineralization to see if changes in the ion transport activity would occur as the cultures develop and begin forming a mineralized matrix. MRPC-1 cells were cultured in chemically defined medium containing ascorbate and Pi, and cultures were specifically analyzed for cellular P, and Ca2+ uptake activities and expression of type II high-capacity Na+-Pi cotransporters. The odontoblast-like phenotype of the cell line was ascertained by monitoring the expression of collagen type I and dentin phosphopoprotein (DPP). Mineralized nodule formation started at day 9 after confluency and then rapidly increased. Ca2+ uptake by the cells showed a maximum during the end of the proliferative phase (days 5-7). Pi uptake declined to a basal level during proliferation and then was up-regulated simultaneously with the onset of mineralization to a level fourfold of the basal uptake, suggesting an initiating and regulatory role for cellular Pi uptake in mineral formation. This up-regulation coincided with a conspicuously increased glycosylation of NaPi-2a, indicating an activation of this Na+-Pi cotransporter. The study showed that MRPC-1 cells express an odontoblast-like phenotype already at the onset of culture, but that to mineralize the collagenous extracellular matrix (ECM) that formed, a further differentiation involving their ion transporters is necessary.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line / Q000378:metabolism; D024042:Collagen Type I / Q000096:biosynthesis; D003470:Culture Media; D003804:Dentin / Q000378:metabolism; D003810:Dentinogenesis / Q000502:physiology*; D006031:Glycosylation; D017136:Ion Transport; D009804:Odontoblasts / Q000378:metabolism*; D009805:Odontogenesis / Q000502:physiology*; D010710:Phosphates / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D051381:Rats; D012964:Sodium / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000378:metabolism; D050608:Sodium-Phosphate Cotransporter Proteins; D050609:Sodium-Phosphate Cotransporter Proteins, Type I; D050610:Sodium-Phosphate Cotransporter Proteins, Type II; D050613:Sodium-Phosphate Cotransporter Proteins, Type IIa; D027981:Symporters / Q000378:metabolism
D024042:Collagen Type I; D003470:Culture Media; D010710:Phosphates; C493556:Slc34a1 protein, rat; D019831:Sodium-Calcium Exchanger; D050608:Sodium-Phosphate Cotransporter Proteins; D050609:Sodium-Phosphate Cotransporter Proteins, Type I; D050610:Sodium-Phosphate Cotransporter Proteins, Type II; D050613:Sodium-Phosphate Cotransporter Proteins, Type IIa; D027981:Symporters; D012964:Sodium; D002118:Calcium