The permeability barrier in mammalian epidermis.
The permeability barrier in mammalian epidermis.
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DOI：
10.1083/jcb.65.1.180
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发表时间：
1975-04
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利用示踪剂和冷冻断裂技术研究了哺乳动物表皮通透屏障的结构基础。将水溶性示踪剂（辣根过氧化物酶、镧、铁蛋白）注射到新生小鼠体内或用葡萄球菌剥脱毒素获取的分离的表皮上层片中。示踪剂通过细胞间隙渗透到颗粒层上层，在那里层状体挤出的内容物阻碍了进一步的渗出。层状内容物最初分隔在小袋中，然后融合形成大片，填充角质层的细胞间隙，掩盖了质膜的外叶。这些有条纹的细胞间隙被周期性的球状扩张所中断。当保存得当时，角质层的间隙比以前所认识到的宽5 - 10倍。颗粒细胞膜的冷冻断裂复制品显示出桥粒、稀疏的质膜颗粒和积累的细胞间片层，但没有紧密连接。断裂的角质层显示出大的、光滑的、多层的断裂面。通过冷冻替代，证明了断裂面在颗粒层从通常的膜内路径转向角质层的细胞间隙。我们得出以下结论：（a）水分流失的主要屏障在颗粒层形成，由层状体的细胞间沉积而非闭锁小带所辅助；（b）在角质层内出现一种新的细胞间冷冻断裂面；（c）角质层的细胞间隙区域包含一个扩大的、结构复杂的、可能富含脂质的区域，它可能在经皮转运中起重要作用。
The structural basis of the permeability barrier in mammalian epidermis was examined by tracer and freeze-fracture techniques. Water-soluble tracers (horesradish peroxidase, lanthanum, ferritin) were injected into neonatal mice or into isolated upper epidermal sheets obtained with staphylococcal exfoliatin. Tracers percolated through the intercellular spaces to the upper stratum granulosum, where further egress was impeded by extruded contents of lamellar bodies. The lamellar contents initially remain segregated in pockets, then fuse to form broad sheets which fill intercellular regions of the stratum corneum, obscuring the outer leaflet of the plasma membrane. These striated intercellular regions are interrupted by periodic bulbous dilatations. When adequately preserved, the interstices of the stratum corneum are wider, by a factor of 5-10 times that previously appreciated. Freeze-fracture replicas of granular cell membranes revealed desmosomes, sparse plasma membrane particles, and accumulating intercellular lamellae, but no tight junctions. Fractured stratum corneum displayed large, smooth, multilaminated fracture faces. By freeze-substitution, proof was obtained that the fracture plane had diverted from the usual intramembranous route in the stratum granulosum to the intercellular space in the stratum corneum. We conclude that: (a) the primary barrier to water loss is formed in the stratum granulosum and is subserved by intercellular deposition of lamellar bodies, rather than occluding zonules; (b) a novel, intercellular freeze-fracture plane occurs within the stratum corneum; (c) intercellular regions of the stratum corneum comprise an expanded, structurally complex, presumably lipid-rich region which may play an important role in percutaneous transport.