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 degrees C, ATP in concentrations of 10(-7) M and greater inhibits arginine vasopressin (AVP)-stimulated osmotic water permeability (P-f) . The P-1-purinergic receptor antagonist 8-phenyltheophylline did not attenuate the inhibitory action of ATP, and the poorly hydrolyzable AT P analogue, 5'-adenylylimidodiphosphate (AMP-PNP), mimicked the effect of ATP, arguing against an effect of ATP on a P-1 receptor or the ''P site.'' Purinergic receptor agonists inhibited AVP-stimulated P-f wit h the following rank order efficacy: ATP = ADP = UTP = AMP-PNP = alpha ,beta-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) M ATP; h owever, 10(-4) M ATP failed to inhibit the hydrosmotic action of forsk olin or 8-bromoadenosine 3',5'-cyclic monophosphate. Pretreatment with the phosphodiesterase inhibitor RO20-1724 or indomethacin did not inh ibit 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 activ ates nucleotide receptors on the CCT, mobilizing intracellular Ca2+, w hich inhibits the hydrosmotic action of AVP.