Ohshima H, Maeda T, Takano Y
Second Department of Oral Anatomy, Niigata University School of Dentistry, Japan.
Anat Rec. 1998 Dec;252(4):519-31. doi: 10.1002/(SICI)1097-0185(199812)252:4<519::AID-AR3>3.0.CO;2-I.
Cytochrome oxidase (CO), one of the membrane-bound mitochondrial enzymes involved in oxidative phosphorylation, reflects the functional activity of mitochondria. Mitochondria in the enamel organ show drastic changes in localization during amelogenesis (Smith. INSERM, 1984;125:273-282). In understanding the functional aspects of the enamel organ, it is essential that one knows the exact CO activity in the respective mitochondria. The present study examines the CO activity of mitochondria in the enamel organ of rat incisors throughout the various stages of amelogenesis using light and transmission electron microscopy. CO activity was examined histochemically according to Seligman et al. (J. Cell. Biol., 1968;38:1-14) in decalcified sections of the upper and lower incisors of the rat. In the secretory stage, half of the mitochondria in the ameloblasts accumulated in the infranuclear region were reactive for CO. Both the population and CO activity of the infranuclear mitochondria of ameloblasts decreased significantly in the later stage where the enamel matrix secretion was almost complete. The CO-reactive mitochondria in the cells of the stratum intermedium (SI) gradually increased in number throughout the secretory stage. In the maturation stage, the ameloblasts contained intensively CO-reactive giant mitochondria in the proximal region and regular sized ones in the distal cytoplasm that were mostly devoid of detectable CO reactivity. The proportion of CO-reactive mitochondria in the supranuclear region and the population of mitochondria in the infranuclear regions of the smooth-ended ameloblasts were significantly higher as compared with the respective values in the ruffle-ended ameloblasts. In the late stages of enamel maturation, ameloblasts containing a large number of ferritin-filled pigment vesicles possessed numerous CO-reactive mitochondria between those vesicles in the supranuclear region, implicating an active role of the ameloblasts in iron transfer into the maturing enamel. The papillary layer cells possessed numerous intensively CO-reactive mitochondria throughout the maturation stage. A stage-related variation in the localization of CO-reactive mitochondria in the enamel organ of rat incisors was quantitatively demonstrated. It is conceivable that maturation stage ameloblasts form a functional unit with the papillary layer cells, and operate in energy-requiring events such as active ion transport to, and water and matrix protein removal from the maturating enamel. A sign of such functional integrity among the types of the enamel organ cells (ameloblasts, cells of SI, cells of stellate reticulum, and outer enamel epithelial cells) cannot be seen in the secretory stage. The secretory ameloblasts may function in matrix formation and calcium regulation in a less cooperative manner with the other cells of the enamel organ as compared to the maturation stage ameloblasts.
细胞色素氧化酶（CO）是参与氧化磷酸化的膜结合线粒体酶之一，反映了线粒体的功能活性。成釉器中的线粒体在釉质形成过程中定位发生剧烈变化（史密斯，法国国家健康与医学研究院，1984年；125:273 - 282）。在了解成釉器的功能方面，了解各线粒体中确切的CO活性至关重要。本研究使用光学显微镜和透射电子显微镜检查大鼠切牙成釉器在釉质形成各个阶段线粒体的CO活性。根据塞利格曼等人（《细胞生物学杂志》，1968年；38:1 - 14）的方法，对大鼠上下切牙的脱钙切片进行组织化学CO活性检测。在分泌期，成釉细胞中积聚在核下区域的线粒体有一半对CO呈反应性。在釉质基质分泌几乎完成的后期，成釉细胞核下线粒体的数量和CO活性均显著降低。中间层（SI）细胞中的CO反应性线粒体在整个分泌期数量逐渐增加。在成熟期，成釉细胞在近端区域含有大量强烈CO反应性的巨大线粒体，而在远端细胞质中则含有大小正常的线粒体，这些线粒体大多没有可检测到的CO反应性。与皱褶缘成釉细胞相比，平滑缘成釉细胞核上区域CO反应性线粒体的比例和核下区域线粒体的数量显著更高。在釉质成熟后期，含有大量充满铁蛋白的色素小泡的成釉细胞在核上区域的这些小泡之间有许多CO反应性线粒体，这表明成釉细胞在将铁转运到成熟釉质中发挥着积极作用。乳头层细胞在整个成熟期都有许多强烈CO反应性的线粒体。定量证明了大鼠切牙成釉器中CO反应性线粒体定位的阶段相关变化。可以想象，成熟阶段的成釉细胞与乳头层细胞形成一个功能单元，并在需要能量的活动中发挥作用，如向成熟釉质进行主动离子转运以及从成熟釉质中去除水和基质蛋白。在分泌期，成釉器细胞类型（成釉细胞、SI细胞、星网状层细胞和外釉上皮细胞）之间这种功能完整性的迹象并不明显。与成熟阶段的成釉细胞相比，分泌期的成釉细胞在基质形成和钙调节方面与成釉器其他细胞的协作可能较少。
