Another barrier to water-soluble drugs is the glial connective tissue cells (astrocytes), which form an astrocytic sheath close to the basement membrane of the capillary endothelium.

• 水溶性药物的另一个屏障是胶质结缔组织细胞（星形细胞），该细胞所形成的星形细胞鞘与毛细血管内皮基膜紧密邻接。