Bronckers A L, Bervoets T J, Lyaruu D M, Wöltgens J H
Department of Oral Cell Biology, ACTA, Vrije Universiteit, Amsterdam, The Netherlands.
Arch Oral Biol. 1989;34(8):625-36. doi: 10.1016/0003-9969(89)90017-4.
Whether the interference by fluoride (F-) with secretory amelogenesis in vitro could be modulated by altering the levels of calcium (Ca) and inorganic phosphate (P) in the medium was investigated. Hamster first upper molar tooth germs in the secretory phase of amelogenesis were exposed to 10 microM-1.31 mM (0.2-25 parts/10(6)) of F- in vitro for 2 days in the presence of either low (1.2 mM), moderate (2.1 mM) or high (4.1 mM) levels of Ca, or moderate (1.6 mM) and high (3.6 mM) levels of P. The biosynthesis and secretion of enamel matrix proteins under each of the experimental conditions were examined by labelling with [3H]-proline during the last 24 h of culture, and mineralization by labelling with 45Ca and [32P]-orthophosphate. With moderate levels of Ca and P (control medium), F- increased the uptake of 45Ca and 32P in a dose-dependent manner; F- did not inhibit the synthesis of matrix proteins but to a moderate extent impaired their secretion. In explants grown in the presence of 52 microM of F- the superficial layers of enamel matrix deposited in vitro (fluorotic matrix) failed to mineralize. Increasing P levels in the medium had no clear histological effect, whereas lowering Ca levels sometimes seemed to aggravate the F- effect. Raising Ca levels improved the histological pattern: in spite of the presence of F-, high Ca levels allowed a limited mineralization of the superficial layer of fluorotic matrix along with a strong rise in mineralization of the deeper layers of pre-exposure enamel. High Ca levels also considerably reduced the cellular changes in secretory ameloblasts induced by 52 microM of F- and slightly counteracted the inhibition of matrix secretion, as measured biochemically. Some of the effects of F- on secretory amelogenesis in vitro can thus be reversed by raising Ca levels in the medium. Therefore, the effect of F- on secretory amelogenesis in vitro seems to be primarily interference with the enamel mineralization process per se and, secondarily, an impairment of matrix secretion.
研究了通过改变培养基中钙（Ca）和无机磷酸盐（P）的水平是否可以调节氟化物（F-）对体外分泌期釉质形成的干扰。处于釉质形成分泌期的仓鼠第一上臼齿牙胚在体外分别暴露于10微摩尔至1.31毫摩尔（0.2至25份/10⁶）的F-中2天，同时培养基中钙的水平分别为低（1.2毫摩尔）、中（2.1毫摩尔）或高（4.1毫摩尔），或者磷的水平分别为中（1.6毫摩尔）和高（3.6毫摩尔）。在培养的最后24小时内用[³H]-脯氨酸标记来检测每种实验条件下釉质基质蛋白的生物合成和分泌，并用⁴⁵Ca和[³²P]-正磷酸盐标记来检测矿化情况。在钙和磷水平适中（对照培养基）时，F-以剂量依赖方式增加了⁴⁵Ca和³²P的摄取；F-并不抑制基质蛋白的合成，但在一定程度上损害了它们的分泌。在含有52微摩尔F-的外植体中，体外沉积的釉质基质表层（氟斑基质）未能矿化。培养基中磷水平的升高没有明显的组织学效应，而钙水平的降低有时似乎会加重F-的影响。提高钙水平改善了组织学模式：尽管存在F-，高钙水平仍使氟斑基质表层有有限的矿化，同时暴露前釉质深层的矿化有显著增加。高钙水平还大大减少了52微摩尔F-诱导的分泌期成釉细胞的细胞变化，并在生化检测中略微抵消了对基质分泌的抑制。因此，通过提高培养基中的钙水平可以逆转F-对体外分泌期釉质形成的一些影响。所以，F-对体外分泌期釉质形成的影响似乎主要是对釉质矿化过程本身的干扰，其次是对基质分泌的损害。
