BEHAVIOR OF CARBONATE AND MAGNESIUM-IONS IN THE INITIAL CRYSTALLITES AT THE EARLY DEVELOPMENTAL STAGES OF THE RAT CALVARIA

Analysis of the contents of calcium (Ca), magnesium (Mg), phosphate, a nd carbonate ions in the mineral phase of rat calvaria specimens obtai ned at different developmental stages indicated that the mineral at th e newborn stage contained a negligible amount of carbonate, but a high content of Mg. There was no significant difference in Ca and phosphat e (as PO4) contents between the newborn material and that from later s tages. A relatively large amount of carbonate was detected in the calv aria from 6-day-old rats, in which only immature crystals were observe d, thus indicating the beginning of apatite formation. Furthermore, us ing laser Raman microprobe analysis we confirmed that the Raman peak a t 1120 cm(-1) band, indicative of a Mg-CO3 compound, appeared at the 6 -day stage. We also observed that the Raman peak at 988 cm(-1) found i n the samples from the newborn seemed to have shifted to 963-962 cm(-1 ) in the case of those obtained from 6-day-old rats, a shift which sug gests the conversion from the non-apatitic to the apatitic form. These results indicate that carbonate ions might facilitate the initiation of crystal development by converting the inhibitory Mg ion into its in active form (Mg-carbonate compound).