Remezal M, Gil-Loyzaga P
Departamento de Ciencias Morfológicas, Facultad de Medicina, Universidad Complutense, Madrid, Spain.
Hear Res. 1993 Mar;66(1):23-30. doi: 10.1016/0378-5955(93)90256-z.
The uptake of D-3H-glucosamine by the developing cochlea of normal and hypothyroid rats was examined using light microscopic radioautography. During postnatal development, normal and hypothyroid rat cochleas exhibited a layer of radiolabelling in the tectorial membrane (TM). This layer first appeared in the TM region which covers the spiral limbus and the Kölliker's organ (KO), then progressively reached the apical part of the TM covering the organ of Corti. Radiolabelling was significantly greater in hypothyroid than in normal cochleas. These findings suggests that the enormous size reached by the TM in the congenital hypothyroidism could be related to an increase of epithelial secretion, at least for carbohydrates. It also suggests that TM, in normal and hypothyroid cochleas, could be formed during development by the addition of successive layers. Older layers could be displaced upwards by the new ones. Cochleas of normal young adult rats, treated with D-3H-glucosamine, showed a very scarce and diffuse radiolabelling. Cochleas of hypothyroid young adult rats exhibited a thickened and distorted TM, which incorporated a significant amount of carbohydrates. These results suggest that TM secretion is highly reduced in young adult normal animals, while in young adult hypothyroid ones it is still active. During cochlear maturation, thyroxine seems to be necessary, not only for the synthesis of normal glycoproteins (as suggested by previous reports), but also for the control of glycoprotein secretion.
利用光学显微镜放射自显影技术，研究了正常和甲状腺功能减退大鼠发育中的耳蜗对D-3H-葡萄糖胺的摄取情况。在出生后的发育过程中，正常和甲状腺功能减退大鼠的耳蜗在盖膜（TM）中均表现出一层放射性标记。这一层首先出现在覆盖螺旋缘和科蒂器（KO）的TM区域，然后逐渐到达覆盖柯蒂氏器的TM顶端部分。甲状腺功能减退大鼠耳蜗中的放射性标记明显高于正常大鼠。这些发现表明，先天性甲状腺功能减退时TM的巨大尺寸可能与上皮分泌增加有关，至少对于碳水化合物来说是这样。这也表明，在正常和甲状腺功能减退的耳蜗中，TM在发育过程中可能是通过相继添加层而形成的。较老的层可能会被新的层向上推移。用D-3H-葡萄糖胺处理的正常成年幼鼠的耳蜗显示出非常稀少且弥散的放射性标记。甲状腺功能减退成年幼鼠的耳蜗表现出TM增厚和扭曲，其中掺入了大量碳水化合物。这些结果表明，成年正常动物的TM分泌高度减少，而成年甲状腺功能减退动物的TM分泌仍然活跃。在耳蜗成熟过程中，甲状腺素似乎不仅对正常糖蛋白的合成是必要的（如先前报道所暗示的），而且对糖蛋白分泌的控制也是必要的。
