Figure 5.

Effect of tolvaptan on free cytosolic calcium content in MDCK cells. (A) MDCKI cells, expressing V2R endogenously, were loaded with 7 μM fura‐2‐AM for 15 min. at 37°C in DMEM. Cells were left under basal conditions (n = 71 cells) or treated with tolvaptan (n = 97 cells) or tolvaptan in the presence of V1a receptor antagonist (SR49059) (n = 60 cells). Data are expressed as means ± S.E.Ms (***P < 0.0001 versus CTR). (B) MDCKI cells were transiently transfected with human V2 receptor, EGFP tagged. Free cytosolic [Ca²⁺] was calculated 48 hrs after transfection. Tolvaptan‐treated cells (n = 27 cells) showed a significant increase in calcium content with respect to untreated cells (n = 20 cells). Data (means ± S.E.Ms) were analysed by Student's t test with **P < 0.0003 considered to be statistically different. (C) MDCK cells clone II, not expressing V2R, were left untreated (n = 76) or stimulated with tolvaptan (n = 107) or with forskolin (n = 30) and subjected to intracellular calcium measurements. Data are expressed as means ± S.E.Ms (**P < 0.001 versus CTR).