title: Lack of effect of extracellular adenosine generation and signaling on renal erythropoietin secretion during hypoxia.
abstract: Previous studies have yielded conflicting results as to whether extracellular adenosine generation and signaling contributes to hypoxia-induced increases in renal erythropoietin (EPO) secretion. In this study, we combined pharmacological and genetic approaches to elucidate a potential contribution of extracellular adenosine to renal EPO release in mice. To stimulate EPO secretion, we used murine carbon monoxide exposure (400 and 750 parts per million CO, 4 h), ambient hypoxia (8% oxygen, 4 h), or arterial hemodilution. Because the ecto-5-nucleotidase (CD73, conversion of AMP to adenosine) is considered the pacemaker of extracellular adenosine generation, we first tested the effect of blocking extracellular adenosine generation with the specific CD73-inhibitor adenosine 5'-(alpha,beta-methylene) diphosphate (APCP) or by gene-targeted deletion of cd73. These studies showed that neither APCP-treatment nor targeted deletion of cd73 resulted in changes of stimulated EPO mRNA or serum levels, although the increases of adenosine levels in the kidney following CO exposure were attenuated in mice with APCP treatment or in cd73(-/-) mice. Moreover, pharmacological studies using specific inhibitors of individual adenosine receptors (A1 AR, DPCPX; A 2A AR, DMPX; A 2B AR, PSB 1115; A3AR, MRS 1191) showed no effect on stimulated increases of EPO mRNA or serum levels. Finally, stimulated EPO secretion was not attenuated in gene-targeted mice lacking A1A(-/-, A2A AR-/-, A2BAR(-/-), or A3AR-/-. Together, these studies combine genetic and pharmacological in vivo evidence that increases of EPO secretion during limited oxygen availability are not affected by extracellular adenosine generation or signaling.
authors.affiliation: Dept. of Pharmacology and Toxicology, Tübingen Univ. Hospital, Wilhelmstr. 56, D-72074 Tübingen, Germany.
authors.forename: Almut
authors.initials: A
authors.lastname: Grenz
authors.forename: Hua
authors.initials: H
authors.lastname: Zhang
authors.forename: Jochen
authors.initials: J
authors.lastname: Weingart
authors.forename: Simone
authors.initials: S
authors.lastname: von Wietersheim
authors.forename: Tobias
authors.initials: T
authors.lastname: Eckle
authors.forename: Juergen
authors.initials: J
authors.lastname: Schnermann
authors.forename: Christoph
authors.initials: C
authors.lastname: Köhle
authors.forename: Doris
authors.initials: D
authors.lastname: Kloor
authors.forename: Christoph H
authors.initials: CH
authors.lastname: Gleiter
authors.forename: Volker
authors.initials: V
authors.lastname: Vallon
authors.forename: Holger K
authors.initials: HK
authors.lastname: Eltzschig
authors.forename: Hartmut
authors.initials: H
authors.lastname: Osswald
mesh_terms: D015720:5'-Nucleotidase / Q000037:antagonists & inhibitors / Q000172:deficiency; D000241:Adenosine / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism*; D000244:Adenosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001158:Arteries / Q000502:physiology; D002248:Carbon Monoxide / Q000494:pharmacology; D004921:Erythropoietin / Q000097:blood / Q000235:genetics / Q000378:metabolism*; D045604:Extracellular Fluid / Q000378:metabolism*; D006438:Hemodilution; D000860:Hypoxia / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D058915:Purinergic P1 Receptor Antagonists; D012333:RNA, Messenger / Q000378:metabolism; D018047:Receptors, Purinergic P1 / Q000172:deficiency; D015398:Signal Transduction
chemical_list: D058915:Purinergic P1 Receptor Antagonists; D012333:RNA, Messenger; D018047:Receptors, Purinergic P1; C523965:alpha,beta-methyleneadenosine 5'-diphosphate; D004921:Erythropoietin; D000244:Adenosine Diphosphate; D002248:Carbon Monoxide; D015720:5'-Nucleotidase; D000241:Adenosine