Detection of erythropoiesis-stimulating agents (ESAs) in equine urine and blood by SAR-PAGE.

Erythropoiesis-stimulating agents (ESAs) have been used in horses for doping purposes to increase the performance of these animals in endurance sports. Currently, ELISA and mass spectrometry methods are used to detect ESA abuse in equines. However, the sarcosyl polyacrylamide gel-electrophoresis (SAR-PAGE) technique could also be used, since its application in human doping control is well established and has proven to be more sensitive. In this work, the SAR-PAGE method was used to detect rHuEPO, NESP, CERA and EPO-Fc in horse blood and urine. The purification technique for human blood using MAIIA kits worked well for horse samples. The major challenge was horse urine immunopurification, which proved difficult due to filter clogging, but heating and cooling of the horse urine followed by filtration in 30-kDa molecular weight cut-off filters solved this problem. The limits of detection (LODs) of 1.3, 1.6, 6.6 and 13.3 pg/mL for rHuEPO, NESP, CERA and EPO-Fc, respectively, obtained in spiked urine and 40, 100, 80 and 400 pg/mL for rHuEPO, NESP, CERA and EPO-Fc, respectively, acquired in spiked blood are lower than the LODs reported in the literature using LC-MS methods. In addition, the presence of ESAs was detected up to 9 days after the administration of microdoses of Hemax (rHuEPO), NESP and CERA in horse blood and urine. SAR-PAGE may be implemented in the routine analysis of horse doping control laboratories for screening and confirmation of ESA abuse, mainly due to its high sensitivity for both matrices compared to published mass spectrometric methods.