A, the volume effect of Hoe 293b alone, which is a slight swelling of the crypt (2.03 ± 0.3 %, n = 5 crypts from 3 mice, n.s.: Student's t test), measured confocally as the change of cross-section area. The basal NKCC activity is decreased in the presence of Hoe 293b (B), but NKCC1 (B) is activated by a rise in intracellular cAMP upon forskolin stimulation in both cases (n = 6–8 crypts from 3–5 mice in each group; *P < 0.05: §Student's unpaired t test, # Student's paired t test).