ATP inhibits the hydrosmotic effect of AVP in rabbit CCT: Evidence for a nucleotide P_2u receptor

In rabbit renal cortical collecting tubule (CCT), perfused in vitro at 38°C, ATP in concentrations of 10^-7 M and greater inhibits arginine vasopressin (AVP)-stimulated osmotic water permeability (P_f). The P₁-purinergic receptor antagonist 8-phenyltheophylline did not attenuate the inhibitory action of ATP, and the poorly hydrolyzable ATP analogue, 5'-adenylylimidodiphosphate (AMP-PNP), mimicked the effect of ATP, arguing against an effect of ATP on a P₁ receptor or the "P site." Purinergic receptor agonists inhibited AVP-stimulated P_f with the following rank order efficacy: ATP = ADP = UTP = AMP-PNP = α,β-methylene-ATP > 2-methylthio-ATP ≫ AMP > adenosine, consistent with the pharmacology of a "nucleotide" receptor subtype. Pertussis toxin pretreatment attenuated the action of 10^-5 and 10^-6 MATP; however, 10^-4 MATP failed to inhibit the hydrosmotic action of forskolin or 8-bromoadeno-sine 3',5'-cyclic monophosphate. Pretreatment with the phosphodiesterase inhibitor RO20-1724 or indomethacin did not inhibit the action of ATP. Staurosporin and 3,4,5-trimethoxybenzoic acid 8-(diethylamino)octyl ester significantly attenuated the inhibition of P_f by lower concentrations of ATP. These data suggest that ATP activates nucleotide receptors on the CCT, mobilizing intracellular Ca²⁺, which inhibits the hydrosmotic action of AVP.