Figure 4. Effect of hypertonic pretreatment on urea-induced caspase activation.

MDCK (open bars) and PI (hatched bars) cells were left untreated (control), exposed to medium containing 400 mm urea for 24 h (+ 400 mm urea) or incubated in hypertonic medium (500 mosmol (kg H₂O)⁻¹ by NaCl addition) for 24 h prior to exposure to medium containing an additional 400 mm urea for 24 h. Means ± s.e.m. for 4–8 experiments; #P < 0.05 versus respective control; *P < 0.05 versus respective +400 mm urea.