Tc. Cox, APICAL REGULATION OF NONSELECTIVE CATION CHANNELS BY ATP IN LARVAL BULLFROG SKIN, The Journal of experimental zoology, 279(3), 1997, pp. 220-227
The apical membrane of larval bullfrog skin contains a nonselective ca
tion channel that can be activated by apically applied amiloride and a
cetylcholine. In our search for other ligands that might activate this
channel, ATP and other purinergics were tested. When ATP (10-1,000 mu
M) was added to the apical side of tadpole skin mounted in a modified
Ussing chamber, there was a transient increase in short circuit curre
nt (Isc). The increase in Isc occurred with either Na or K as the domi
nant cation in the apical solution. The response was larger in a calci
um-free Ringer. ADP and AMP had similar but smaller effects than ATP.
Adenosine and UTP were without effect. The ATP response was blocked by
W-7, atropine, curare, diltiazem, and suramin. These blockers also in
hibit amiloride stimulation of Isc, suggesting that ATP activates a re
lated transport pathway. Studies with analogs of ATP suggest that the
ATP binding site in tadpole skin has characteristics in common with th
e P2x receptor found in other tissues. These results demonstrate that
in addition to amiloride and acetylcholine, ATP stimulates cation tran
sport at the apical membrane of larval amphibian skin epithelia. (C) 1
997 Wiley-Liss, Inc.