Mechanisms for cell volume regulation of Slick K+ channels.

Slick channels were co-expressed with AQP1 in Xenopus laevis oocytes and the channels were activated by depolarizations to +80 mV for 500 ms (holding potential: −80 mV). In all cases, the maximal currents (at the end of the depolarization period) were measured in isotonic, hypotonic and hypertonic media and are shown as relative changes in the current during cell swelling (hatched bars) and shrinkage (horizontal bars) as compared to the current under isotonic conditions (open bar). The figures show the effect of (A) cytochalasin D (10 µM, preincubation 24 hours), (B) Brefeldin A (10 µM, preincubation 8 hours), (C) Apyrase (5 U/ml) and (D) ATP (100 µM). All values are given as means ±SEM (n = 6–8).