Enhancement of erythropoietin production by selective adenosine A2 receptor agonists in response to hypoxia.
The purpose of this study was to characterize the effects of two new adenosine A2 agonists, 2-(p-(2-carboxyethyl)phenethyl amino)-5'-N-ethylcarboxamidoadenosine (CGS-21680) and N6-(2(3,5-dimethoxyphenyl)-2-(2-methylphenyl)ethyl)-adenosine (DPMA), on erythropoietin (EPO) production in vivo and in vitro. Intravenous injections of CGS-21680 (100 to 500 nmol/kg mouse/day) and DPMA (50 to 500 nmol/kg mouse/day) for 4 days produced significant increases in serum levels of EPO in exhypoxic polycythemic mice. CGS-21680 (10(-7) to 10(-6) mol/L) and DPMA (10(-8) to 10(-5) mol/L) also produced significant increases in medium levels of EPO in a cloned EPO-producing Hep3B hepatocellular carcinoma cell line after 18 hours of incubation in 1% O2. Both compounds also increased cellular cAMP levels significantly in a dose-dependent manner after 1 hour of incubation. A2 receptor binding assays with tritiated CGS-21680 revealed a single type of adenosine receptor binding site on Hep3B cell membranes with a dissociation constant of 132.9 nmol/L and a binding capacity of 270.6 fmol/mg protein. The Ki competition binding values versus tritiated CGS-21680 were 217 nmol/L for CGS-21680 and 86.8 nmol/L for DPMA. These results indicate that adenosine A2 receptor activation amplifies EPO production in response to hypoxia, both in vivo and in vitro.
Ohigashi
T
T
Department of Pharmacology, Tulane University School of Medicine, New Orleans, LA 70112, USA.
Nakashima
J
J
Aggarwal
S
S
Brookins
J
J
Agrawal
K
K
Fisher
J W
JW
D000241:Adenosine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001667:Binding, Competitive; D006528:Carcinoma, Hepatocellular / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D004921:Erythropoietin / Q000096:biosynthesis*; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000097:blood*; D007700:Kinetics; D008113:Liver Neoplasms / Q000378:metabolism; D051379:Mice; D010627:Phenethylamines / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*; D011086:Polycythemia / Q000097:blood*; D058906:Purinergic P1 Receptor Agonists; D014407:Tumor Cells, Cultured
D010627:Phenethylamines; D058906:Purinergic P1 Receptor Agonists; D004921:Erythropoietin; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; C056426:CGS 24012; D000242:Cyclic AMP; D000241:Adenosine