Raviola E, Goodenough D A, Raviola G
J Cell Biol. 1980 Oct;87(1):273-9. doi: 10.1083/jcb.87.1.273.
The structure of gap junctions in the rabbit ciliary epithelium, corneal endothelium, and mouse stomach and liver was studied with the freeze-fracturing technique after rapid freezing to near 4 degrees K from the living state. In the ciliary epithelium, the connexons were randomly distributed, separated by smooth membrane matrix. In the corneal endothelium, both random and crystalline arrangements of the connexons were observed. In the stomach and liver, the connexons were packed but not crystalline. Experimental anoxia or lowered pH caused crystallization of the connexons within 20-30 min. In the ciliary epithelium, the effects of prolonged anoxia or low pH could not be reversed . In addition, invaginated or annular gap junctions increased in number, but their connexons were usually distributed at random. Rapid freezing thus demonstrates that gap junctions of different tissues are highly pleiomorphic in the living state, and this may explain their variations in structure after chemical fixation. The slow time-course and irreversibility of the morphological changes induced by prolonged anoxia or low pH suggest that connexon crystallization may be a long-term consequence rather than the morphological correlate of the switch to high resistance.
利用冷冻断裂技术，在从活体状态快速冷冻至接近4K的条件下，研究了兔睫状上皮、角膜内皮以及小鼠胃和肝脏中缝隙连接的结构。在睫状上皮中，连接子随机分布，被光滑的膜基质分隔。在角膜内皮中，观察到连接子的随机排列和晶体状排列。在胃和肝脏中，连接子紧密排列但并非晶体状。实验性缺氧或pH值降低会在20 - 30分钟内导致连接子结晶。在睫状上皮中，长时间缺氧或低pH值的影响无法逆转。此外，内陷或环状缝隙连接数量增加，但其连接子通常随机分布。因此，快速冷冻表明不同组织的缝隙连接在活体状态下具有高度多形性，这可能解释了它们在化学固定后结构的变化。长时间缺氧或低pH值诱导的形态学变化的缓慢进程和不可逆性表明，连接子结晶可能是一种长期后果，而非转变为高电阻的形态学关联。
