CD73/ecto-5'-nucleotidase, which catalyzes the conversion of adenosine monophosphate to adenosine, has been implicated in vascular homeostasis. The aim of the present study was to evaluate the role of CD73 in erythropoietin (EPO) production and to determine its influence on basal kidney perfusion using a CD73 knockout mutant recently generated by us. Of all organs investigated, kidneys showed the most prominent CD73 activity, preferentially located in peritubular fibroblasts of the renal cortex and the glomerular mesangium. In the absence of CD73, alkaline phosphatase remained unchanged, but tissue adenosine was reduced under control conditions (by 76%) and during normobaric hypoxia (by 72%). Despite the loss of CD73 activity, EPO mRNA and plasma protein concentrations were not different under basal conditions as well as after normobaric hypoxia (8% O2) and carbon monoxide (0.1% CO) inhalation (both for 4 h). Although there were no differences in blood pressure and urine flow volume, average weight of both kidneys was reduced by 21% in the knockout (wild type 7.17+/-1.18 mg g-1 body wt, CD73-/- 5.70+/-1.91 mg g-1 body wt). Measurement of renal plasma flow and glomerular filtration revealed no significant differences when related to respective kidney weights. We conclude that adenosine derived by the extracellular CD73 pathway has no impact on EPO production under basal conditions and after hypoxic challenge but may determine kidney weight.