Detection of recombinant human erythropoietin in urine by isoelectric focusing.

BACKGROUND

Doping with erythropoietic proteins such as recombinant human erythropoietin (rHuEPO) and darbepoetin alfa is a serious issue in sport. There is little information on the time course of detection of rHuEPO in urine and on methods to evaluate electrophoresis-based data.

METHODS

We used a recently described isoelectric focusing method for detecting rHuEPO and endogenous EPO in urine obtained from individuals treated with placebo or epoetin alfa. The latter was administered subcutaneously at 50 IU/kg on days 0, 2, 4, 7, 9, 11, 14, 16, and 18. Blood and urine samples were collected during the morning of study days -3, 0, 2, 4, 7, 9, 11, 14, 16, and 18 and on days 2, 3, 4, and 7 postadministration. We developed visual and numerical (two-band ratio) techniques to evaluate the electropherograms for the presence of rHuEPO.

RESULTS

Compared with the placebo group, the epoetin alfa-treated group responded with increases in hematocrit, reticulocytes, macrocytes, serum EPO, and serum soluble transferrin receptor. The electropherograms showed that the pattern of bands arising from urinary rHuEPO is different from that of endogenous urinary EPO. Both the two-band ratio and the visual technique detected rHuEPO in all 14 epoetin alfa-treated individuals 3 days after the last dose. On the 7th day after the last dose, both techniques detected rHuEPO in approximately one-half of the participants. rHuEPO was not detected in the placebo-treated individuals.

CONCLUSIONS

The isoelectric focusing method detects rHuEPO in most urine samples collected 3 days after nine doses of epoetin alfa. The numerical two-band ratio was equivalent to a visual method for detecting rHuEPO in urine.