In human and rat lung membranes [S-35]GTP gamma S binding is a tool for pharmacological characterization of G protein-coupled dinucleotide receptors

The P2Y receptor family is activated by extracellular nucleotides such as A TP and UTP. P2Y receptors regulate physiological functions in numerous cell , types. In lung, the P2Y(2) receptor subtype plays a role in controlling C l- and fluid transport. Besides ATP or UTP, also diadenosine tetraphosphate (Ap(4)A), a stable nucleotide, seems to be of physiological importance. In membrane preparations from human and rat lung we applied several diadenosi ne polyphosphates to investigate whether they act as agonists for G protein -coupled receptors. We assessed this by determining the stimulation of [S-3 5]GTP gamma S binding. Stimulation of [S-35]GTP gamma S binding to G protei ns has already been successfully applied to elucidate agonist binding to va rious G protein-coupled receptors. Ap(n)A (n = 2 to 6) enhanced [S-35]GTP g amma S binding similarly in human and rat lung membranes, an indication of the existence of G protein-coupled receptor binding sites specific for diad enosine polyphosphates. Moreover, in both human and rat lung membranes comp arable pharmacological properties were found for a diadenosine polyphosphat e ([H-3]Ap(4)A) binding site. The affinity for Ap(2)A, Ap(3)A, Ap(4)A, Ap(5 )A, and Ap(6)A was also comparable. 8-Diazido-Ap(4)A and ATP were less pote nt, whereas the pyrimidine nucleotide UTP showed hardly any affinity. Thus, we present evidence that different diadenosine polyphosphates bind to a co mmon G protein-coupled receptor binding site in membranes derived either fr om human or rat lung. (C) 1999 Elsevier Science Inc.