Introduction + + 1 2 3 5 Xenopus 6 7 − − I sc 2 3 5 8 2 + I sc I sc 2 − 6 9 I sc I sc 2 2 I sc − − 10 − 11 12 13 14 + 15 16 17 − − i − i − + − − i 10 − 18 − i − i I sc I sc − + 19 Materials and methods Cell culture 2 5 2 + Ussing chamber experiments 2 4 3 2 2 2 2 1 I sc 2 V te 2 10 1 1 I sc I sc I sc I sc I sc I sc V te I sc Fig. 1 a V te te I V te I sc b c 2 2  Bioluminescence detection of ATP release 20 Data analysis and statistics P t R I sc I sc r Materials All chemicals were obtained from Sigma-Aldrich (St. Louis, MO, USA) unless otherwise noted. Results sc I sc I sc + I sc 2 2 I sc I sc 2 2 I sc 2 I sc R P I sc R P I sc I sc Fig. 2 I sc I sc A B  arrow G te I sc  3 I sc I sc 3 3 I sc 3 I sc 3 3 3 I sc I sc R P Fig. 3 I sc  lower bar a b upper bar  4 I sc I sc I sc I sc I sc 2  n  n I sc Fig. 4 I sc I sc I sc open circles  solid line 1 solid dots  dashed line 2 I sc I sc r P r P  2+ I sc 5 I sc I sc − − 2+ − I sc 5 I sc 5 5 − Fig. 5 I sc A  lowest bar I sc  middle  upper bars Gliben B  A I sc  A  point 2  point 3 point 4 P I sc P C D E change I sc I sc point 2  A  C  D point 3  B  C n  D n  B P  − 10 2+ 2+ i 21 I sc 2+ I 22 23 2+ 22 6 I sc I sc 6 I sc 6 Fig. 6 I sc A I sc TG-initial TG-late I sc P I sc P B change I sc gray bars open bars  A P  I sc 1 I sc I sc 1 7 7 I sc I sc 7 I sc 2 2 P I sc 2 2 P I sc I sc Fig. 7 I sc A B  A C  A  B  A P  I sc + − 2+ 24 25 2+ I sc 8 I sc 8 26 8 I sc 2 I sc 2 P 2 P 2 n 2 n Fig. 8 I sc A I sc B I sc  I sc I sc I sc I sc 9 I sc 9 9 I sc I sc 2 2 P I sc 2 2 P I sc I sc Fig. 9 I sc A B C I sc Basal-I sc I sc AS-I sc I sc DS-I sc  Measurement of ATP released from MDCK cells 20 10 n P n P n P Fig. 10 n n basal cAMP n Sham, n P  Discussion 10 F F F 2 − + I sc I sc I sc I sc 2 3 I sc I sc I sc I sc I sc 2 6 9 27 3 2 − I sc I sc − + 2 I sc 3 I sc I sc 4 I sc I sc I sc I sc I sc I sc − I sc 2 I sc − − I sc 5 + 28 29 + 10 30 − − − 31 32 − I sc I sc 10 I sc 6 2+ i 22 I sc 33 2+ i 21 I sc 34 35 36 + I sc I sc 7 I sc 7 I sc I sc 9 I sc I sc I sc 2+ 2+ - 24 37 38 + 39 41 42 44 − 14 45 46 47 10 8 2+ − 8 10 48 I sc I sc 43 42 49 49 50 51 50 2+ i 11 Fig. 11 + − + + Isc + te − − − - − I sc 46 − Isc I sc  Implications for renal pathophysiology + − 42 43 49 48 + + 19 + − 19 52