Fig. 3.

The relative unit water permeability of M1 and M23 in transfected human bronchial epithelial cell line. a The level of GFP fluorescence within the cells. b Loading with calcein, which was used for water permeability measurements, was similar in AQP4-positive and AQP4-negative cells. Numbers indicate the same cells before (a) and after (b) calcein loading. c Single cell traces showing the dilution of calcein due to the cell swelling after an osmotic challenge. In cells with low GFP (and hence AQP4) expression (cells 1–3 in a), the swelling rate was increasing (line 1 through line 3 in c) with the increase in GFP (AQP4) level. The swelling of the cells 3 and 4 occurred at practically identical speed, probably due to saturation of the plasma membrane with AQP4. d Maximal relative water permeability in cells expressing M1 (n = 22) and M23 (n = 13), **P < 0.01