%0 Journal Article %1 Ukena1984 %A Ukena, D. %A Furler, R. %A Lohse, M. J. %A Engel, G. %A Schwabe, U. %D 1984 %J Naunyn Schmiedebergs Arch Pharmacol %K & Adenosine/*analogs Adenylate Adipose Animals Assay Cell Cyclase/analysis Iodine Lipolysis Membrane/analysis Phenylisopropyladenosine/*analogs Purinergic Radioisotopes Radioligand Rats Surface/*analysis/metabolism Tissue/cytology/*metabolism Tritium derivatives/antagonists derivatives/metabolism inhibitors Receptor %N 3 %P 233-40 %T Labelling of Ri adenosine receptors in rat fat cell membranes with (-)-125iodoN6-hydroxyphenylisopropyladenosine %U http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=6089004 %V 326 %X A new adenosine analogue, (-)-iodo-N6-phydroxyphenylisopropyladenosine (-)-IHPIA, has been developed for radioligand binding studies of Ri adenosine receptors. In addition, the effects of (-)IHPIA on adenosine-mediated responses of rat fat cells have been characterized. (-)IHPIA is slightly less potent at Ri adenosine receptors than (-)N6-phenylisopropyladenosine (-)PIA as assessed by adenylate cyclase and lipolysis studies. (-)IHPIA inhibited basal adenylate cyclase activity with an IC50 of 60 nmol/l compared to an IC50 of 16.3 nmol/l for (-)PIA. (-)PIA and (-)IHPIA inhibited adenosine deaminase-stimulated lipolysis of intact rat fat cells with an IC50 of 0.55 and 3.6 nmol/l. The potency of (-)N6-phydroxyphenylisopropyladenosine (-)HPIA was intermediate. (-)HPIA has been labelled with carrier-free Na125I to very high specific activity (2,175 Ci/mmol) and used as agonist radioligand in binding studies of Ri adenosine receptors. The binding of (-)125IHPIA was saturable, reversible and stereospecific. Saturation analysis revealed two affinity states with dissociation constants (KD) of 0.7 and 7.6 nmol/l and maximal number of binding sites (Bmax) of 0.94 and 0.95 pmol/mg protein. The rate constant of association, k1, was 3.7 X 10(8) l X mol-1 X min-1. Binding was slowly reversible with a t1/2 of 88 min. In competition experiments specific binding was most potently inhibited by (-)PIA, N6-cyclohexyladenosine (CHA), (-)HPIA and (-)IHPIA, followed by 5'-N-ethylcarboxamidoadenosine (NECA) and 2-chloroadenosine. 1,3-Diethyl-8-phenylxanthine (DPX) and 8-phenyltheophylline were the most potent adenosine antagonists with Ki-values of 67 and 83 nmol/l, whereas the methylxanthines 3-isobutyl-1-methylxanthine, theophylline and caffeine had Ki-values between 1 and 21 mumol/l.(ABSTRACT TRUNCATED AT 250 WORDS)

@article{Ukena1984, abstract = {A new adenosine analogue, (-)-iodo-N6-phydroxyphenylisopropyladenosine [(-)-IHPIA], has been developed for radioligand binding studies of Ri adenosine receptors. In addition, the effects of (-)IHPIA on adenosine-mediated responses of rat fat cells have been characterized. (-)IHPIA is slightly less potent at Ri adenosine receptors than (-)N6-phenylisopropyladenosine [(-)PIA] as assessed by adenylate cyclase and lipolysis studies. (-)IHPIA inhibited basal adenylate cyclase activity with an IC50 of 60 nmol/l compared to an IC50 of 16.3 nmol/l for (-)PIA. (-)PIA and (-)IHPIA inhibited adenosine deaminase-stimulated lipolysis of intact rat fat cells with an IC50 of 0.55 and 3.6 nmol/l. The potency of (-)N6-phydroxyphenylisopropyladenosine [(-)HPIA] was intermediate. (-)HPIA has been labelled with carrier-free Na[125I] to very high specific activity (2,175 Ci/mmol) and used as agonist radioligand in binding studies of Ri adenosine receptors. The binding of (-)[125I]HPIA was saturable, reversible and stereospecific. Saturation analysis revealed two affinity states with dissociation constants (KD) of 0.7 and 7.6 nmol/l and maximal number of binding sites (Bmax) of 0.94 and 0.95 pmol/mg protein. The rate constant of association, k1, was 3.7 X 10(8) l X mol-1 X min-1. Binding was slowly reversible with a t1/2 of 88 min. In competition experiments specific binding was most potently inhibited by (-)PIA, N6-cyclohexyladenosine (CHA), (-)HPIA and (-)IHPIA, followed by 5'-N-ethylcarboxamidoadenosine (NECA) and 2-chloroadenosine. 1,3-Diethyl-8-phenylxanthine (DPX) and 8-phenyltheophylline were the most potent adenosine antagonists with Ki-values of 67 and 83 nmol/l, whereas the methylxanthines 3-isobutyl-1-methylxanthine, theophylline and caffeine had Ki-values between 1 and 21 mumol/l.(ABSTRACT TRUNCATED AT 250 WORDS)}, added-at = {2010-12-14T18:12:02.000+0100}, author = {Ukena, D. and Furler, R. and Lohse, M. J. and Engel, G. and Schwabe, U.}, biburl = {https://www.bibsonomy.org/bibtex/223fb29f93379be8961e0076f34d5d4e4/pharmawuerz}, endnotereftype = {Journal Article}, interhash = {22c9c23c4466aeecec8fbf041b860c6e}, intrahash = {23fb29f93379be8961e0076f34d5d4e4}, issn = {0028-1298 (Print) 0028-1298 (Linking)}, journal = {Naunyn Schmiedebergs Arch Pharmacol}, keywords = {& Adenosine/*analogs Adenylate Adipose Animals Assay Cell Cyclase/analysis Iodine Lipolysis Membrane/analysis Phenylisopropyladenosine/*analogs Purinergic Radioisotopes Radioligand Rats Surface/*analysis/metabolism Tissue/cytology/*metabolism Tritium derivatives/antagonists derivatives/metabolism inhibitors Receptor}, month = Jun, note = {Ukena, D Furler, R Lohse, M J Engel, G Schwabe, U In Vitro Germany, west Naunyn-Schmiedeberg's archives of pharmacology Naunyn Schmiedebergs Arch Pharmacol. 1984 Jun;326(3):233-40.}, number = 3, pages = {233-40}, shorttitle = {Labelling of Ri adenosine receptors in rat fat cell membranes with (-)-[125iodo]N6-hydroxyphenylisopropyladenosine}, timestamp = {2010-12-14T18:20:09.000+0100}, title = {Labelling of Ri adenosine receptors in rat fat cell membranes with (-)-[125iodo]N6-hydroxyphenylisopropyladenosine}, url = {http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=6089004}, volume = 326, year = 1984 }