Landis D M, Weinstein L A, Skordeles C J
Department of Neurology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106.
Glia. 1991;4(4):335-44. doi: 10.1002/glia.440040402.
Astrocytic processes investing vascular structures or forming the surface of mammalian brain have large numbers of orthogonally packed aggregates of intramembrane particles, termed "assemblies." Similar particle aggregates are expressed by astrocytes derived from neonatal rat forebrain in secondary culture, but they are much more uniformly distributed across the membranes of the cultured cells. Dexamethasone, a potent glucocorticoid, affects the differentiation of astrocyte membrane structure in two patterns, depending on the rate of proliferation in the culture. When confluent secondary cultures of astrocytes are exposed to 5 microM dexamethasone, the densities of assemblies increase, and in some cells approach the values present in the glial limitans in vivo. However, when rapidly proliferating astrocytes are exposed to dexamethasone during the first week of secondary culture, most of the astrocytes fail to express any assemblies. The rate of astrocyte proliferation is slowed, and a lower cell density is reached during the first 2 weeks of secondary culture in dexamethasone. The suppression of assemblies is transient: as the cultures approach confluence, the proportion of cells expressing assemblies increases to nearly control levels, and the density of assemblies increases to greater than control values in some astrocytes. Certain of the effects of dexamethasone on cultured astrocytes may have relevance for understanding the mechanism(s) of its action in treating cerebral edema.
包绕血管结构或构成哺乳动物脑表面的星形胶质细胞突起含有大量呈正交排列的膜内颗粒聚集体，称为“集合体”。源自新生大鼠前脑的星形胶质细胞在传代培养时也表达类似的颗粒聚集体，但它们在培养细胞的膜上分布更为均匀。地塞米松是一种强效糖皮质激素，根据培养中的增殖速率，它以两种模式影响星形胶质细胞膜结构的分化。当星形胶质细胞的汇合传代培养物暴露于5微摩尔地塞米松时，集合体的密度增加，并且在一些细胞中接近体内胶质界膜中的值。然而，当快速增殖的星形胶质细胞在传代培养的第一周暴露于地塞米松时，大多数星形胶质细胞不表达任何集合体。星形胶质细胞的增殖速率减慢，并且在传代培养的前2周内在地塞米松中达到较低的细胞密度。集合体的抑制是短暂的：随着培养物接近汇合，表达集合体的细胞比例增加到接近对照水平，并且在一些星形胶质细胞中集合体的密度增加到大于对照值。地塞米松对培养星形胶质细胞的某些作用可能与理解其治疗脑水肿的作用机制有关。
