Freeze-fracture replicas from TR-CSFB cells (A) and Z310 cells (B-D) treated with 1 μM dexamethsone (dexa. A, D) and 100 nM (B) and 550nM (C) hydrocortisone (HC). Whereas the TR-CSFB cells (A), but not the Z310 cells (D), have been partly induced by dexamethasone to form tight junctions (TJs), the Z310 cells (B,C), but not the TR-CSFB cells (not shown), can be induced by hydrocortisone to form some TJs. Arrows point to TJs particles in all pictures. EF: external fracture face, PF: protoplasmic fracture face.