Modulation of erythropoietin production by adenosine.

Adenosine is an important regulatory molecule that increases in hypoxic and ischemic tissues and has been proposed to mediate blood flow in response to oxygen availability. The current study ascribes another oxygen-responsive role to adenosine, that of regulating synthesis of the erythropoiesis-stimulating hormone, erythropoietin. When perfused through isolated rat kidneys, exogenous adenosine in nanomolar concentrations increased erythropoietin production, whereas inosine, the deaminated nucleoside, had no effect. In addition, an adenosine antagonist, and adenosine deaminase, diminished erythropoietin titers in renal perfusates. In intact rats, adenosine deaminase injections followed by a hypoxic stimulus slightly reduced erythropoietin serum concentrations, whereas an adenosine deaminase inhibitor sharply increased erythropoietin titers. The results suggest that adenosine may function as a mediator to link oxygen supply with erythropoietin production.