FIG. 6.

Transepithelial resistance promptly decreases in response to the addition of water or 1.5 mM EGTA to the apical surface. Water or EGTA was applied for 20 min. Arrow A indicates addition of vector buffer to the apical surface after the 20-min treatment with water or EGTA. Arrow B indicates removal of apical solution at 4 h. The fall in resistance was reversible over a 16- to 18-h period. Control epithelia (dotted line) showed no change in transepithelial resistance over a similar time. Each point represents the mean ± SE for three epithelial cell membranes.