Abstract
This study characterizes the receptor binding and functional effects of CVT-3619 [2-{6-[((1R,2R)-2-hydroxycyclopentyl)-amino]purin-9-yl}(4S,5S,2R,3R)-5-[(2-fluorophenylthio)methyl]-oxolane-3,4-diol], a novel N6-5′ -substituted adenosine analog and A1 -adenosine receptor (A AdoR) agonist, on rat epididymal and inguinal adipocytes and on the isolated heart and compares these effects with those caused by the full agonist N6 -cyclopentyladenosine (CPA). In addition, the hypothesis that adipocyte A1AdoR are a heterogeneous population with regard to their affinities for ligands was tested. CVT-3619 was 10–100-fold selective for A1AdoR versus other AdoR and bound to adipocyte membranes with high (KH = 14 nM) and low (K = 5.4 μM) affinities. CVT-3619 reduced cyclic AMP content and release of nonesterified fatty acids from epididymal adipocytes with IC50 values of 6 and 44 nM, respectively. CVT-3619 was a partial agonist relative to CPA to reduce lipolysis in epididymal and inguinal adipocytes. CVT-3619 did not change atrial rate in rat heart and caused a small (6-ms) prolongation of the stimu-lus-to-His bundle interval without causing atrioventricular block in guinea pig heart (effects mediated by A1AdoR), whereas CPA caused atrioventricular block and near cessation of atrial electrical activity. CVT-3619 increased coronary conductance (effect mediated by A2AAdoR) only at concentrations ≥10 μM. Rat epididymal adipocyte A1AdoR had similar affinities for the antagonist 8-cyclopentyl-1,3-dipropylxanthine in the presence of three dissimilar A AdoR agonists (2-chloro-N6 -cyclopentyladenosine, N6 -sulfophenyladenosine, and N-5′ -ethylcarboxamidoadenosine) as determined by Schild analysis. It was concluded that rat epididymal adipocyte A1AdoR are a homogeneous receptor population with regard to affinities for ligands and that CVT-3619 is a partial agonist with selectivity for A1AdoR and inhibition of lipolysis.
Footnotes
-
This project was supported in part by Grant 56747 from National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (J.C.S.).
-
doi:10.1124/jpet.105.099119.
-
ABBREVIATIONS: A1AdoR, A1-adenosine receptor(s); ADA, adenosine deaminase; BSA, bovine serum albumin; CCPA, 2-chloro-N6 -cyclopentyladenosine; HEK, human embryonic kidney; CPA, N6 -cyclopentyladenosine; CPX, 8-cyclopentyl-1,3-dipropylxanthine; CVT-3619, 2-{6-[((1R,2R)-2-hydroxycyclopentyl)amino]purin-9-yl}(4S,5S,2R,3R)-5-[(2-fluorophenylthio)methyl]oxolane-3,4-diol; EHNA, erythro-9-(2-hydroxy-3-nonyl)-adenine; KRH, Krebs-Ringer-HEPES; MRE3008F20, 5N-(4-methoxyphenylcarbamoyl)amino-8-propyl-2-(2-furyl)pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine; NECA, 5′-N-ethylcarboxamidoadenosine; NEFA, nonesterified fatty acid; S-H, stimulus to His bundle; SPA, N6-sulfophenyladenosine; TE, Tris-EDTA; ZM241385, 4-(2-[7-amino-2-(2-furyl)[1,2,4]triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethyl)phenol; CHO, Chinese hamster ovary; PCR, polymerase chain reaction.
- Received November 25, 2005.
- Accepted January 9, 2006.
- The American Society for Pharmacology and Experimental Therapeutics
JPET articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|