title: Adenosine receptors of human leukocytes--II. Characterization of an inhibitory P-site.
abstract: We have investigated the effects of 2',5'-dideoxyadenosine (DDA), 9'-beta-D-arabinofuranosyladenine (ARA), and 9-beta-D-xylofuranosyladenine (XFA), which have been classified as P-site adenosine agonists, on the cyclic adenosine 3',5'-monophosphate (cAMP) metabolism of human lymphocytes and polymorphonuclear leukocytes (PMNs). DDA (10(-5)-2 x 10(-4) M), ARA and XFA caused a dose-dependent decrease in cAMP content of human lymphocytes. In addition to decreasing lymphocyte cAMP levels, DDA, ARA, and XFA markedly inhibited the effects of many adenylate cyclase-stimulating agents including beta-adrenergic stimuli, prostaglandin E1 (PGE1), histamine, adenosine, forskolin and cholera toxin. Theophylline and 3-isobutyl-1-methylxanthine, which are known antagonists of adenosine A1/Ri and A2/Ra receptors, did not modify the inhibiting effects of DDA. Mn2+ (1 mM) increased the sensitivity to inhibition of adenylate cyclase agonists by DDA. We also search for the presence of adenosine P-sites in human PMNs. DDA caused a significant decrease of PMN cAMP levels only at the highest concentrations used (2 x 10(-4) M). In contrast, even low concentrations of DDA (10(-6)-10(-4) M) concentration-dependently blocked the stimulatory effect of PGE1 and forskolin on PMN cAMP accumulation. The results support the existence of a purine P-site that regulates cAMP metabolism of human lymphocytes and PMNs.
authors.affiliation: Department of Medicine, University of Naples Federico II, II School of Medicine, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Marone
authors.forename: R
authors.initials: R
authors.lastname: Petracca
authors.forename: S
authors.initials: S
authors.lastname: Vigorita
authors.forename: V
authors.initials: V
authors.lastname: Casolaro
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000378:metabolism; D000328:Adult; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D016048:Dideoxyadenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D008214:Lymphocytes / Q000187:drug effects* / Q000378:metabolism; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism; D058914:Purinergic Antagonists; D011983:Receptors, Purinergic / Q000187:drug effects / Q000378:metabolism*; D014740:Vidarabine / Q000494:pharmacology
chemical_list: D058914:Purinergic Antagonists; D011983:Receptors, Purinergic; C014251:9-xylosyladenine; D016048:Dideoxyadenosine; C021008:2',5'-dideoxyadenosine; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D014740:Vidarabine; D000241:Adenosine