Takano Y, Hanawa M, Yamamoto T, Domon T, Fujinami H, Hanaizumi Y, Wakita M
Department of Oral Anatomy II, Hokkaido University School of Dentistry, Sapporo, Japan.
J Biol Buccale. 1990 Jun;18(2):135-47.
The distribution and movement of calcium through the enamel organ and into the forming enamel was examined by means of quantitative 45Ca radioautography in rat incisors. Dislocation of radiocalcium in the specimen was minimized during histologic and radioautographic processing by using rapid freeze/freeze-substitution and dry emulsion coating methods. At 30 sec. after the 45Ca injection, distinct peaks of radioactivity occurred in the connective tissue immediately adjacent to the enamel organ and the infranuclear compartment of secretory ameloblasts. An intense labeling also occurred in the superficial layers of the forming enamel extending 15 microns below the surface. The grain density in the distal cytoplasm of secretory ameloblasts increased at later time periods, whereas all other regions of the enamel organ showed a considerable decrease in radioactivity. The radioactivity in the infranuclear compartment of ameloblasts with numerous mitochondria remained relatively high at 2 min. but was abolished by 10 min. after the injection. The grain density in the enamel matrix became much stronger but the labeled regions only extended to 20, 30, and 40 microns below the surface at 2, 10, and 60 min. after the injection, respectively. The application of wet emulsion over similarly prepared sections caused a severe dislocation of radiocalcium in the specimens. These data confirmed the rapid penetration of systemically administered radiocalcium into the surface layers of forming enamel and its slow diffusion to the deeper layers. The time-related changes in relative grain densities at various regions of the ameloblasts support the coexistence of a relatively slow transcellular pathway for calcium through the secretory ameloblast layer.
通过对大鼠切牙进行定量⁴⁵Ca放射自显影，研究了钙在釉器中的分布及进入正在形成的釉质的移动情况。在组织学和放射自显影处理过程中，采用快速冷冻/冷冻置换和干乳剂包被方法，将标本中放射性钙的移位降至最低。在注射⁴⁵Ca后30秒，紧邻釉器的结缔组织以及分泌成釉细胞的核下区出现明显的放射性峰值。在正在形成的釉质表面层下方15微米范围内也出现强烈标记。分泌成釉细胞远端细胞质中的颗粒密度在后期增加，而釉器的所有其他区域放射性显著降低。含有大量线粒体的成釉细胞核下区在注射后2分钟时放射性仍相对较高，但在10分钟时消失。釉质基质中的颗粒密度在注射后2分钟、10分钟和60分钟时分别变得更强，但标记区域仅分别延伸至表面下方20微米、30微米和40微米处。在类似制备的切片上应用湿乳剂会导致标本中放射性钙严重移位。这些数据证实了全身给予的放射性钙能迅速穿透正在形成的釉质表层，并缓慢扩散至较深层。成釉细胞不同区域相对颗粒密度随时间的变化支持钙通过分泌成釉细胞层存在相对缓慢的跨细胞途径。
