KEELEY, K.O.; KREFT, J.M.; NAUSEEF*, J.T.*; REYNOLDS, L.W.; HAUSSMANN, M.; HIEBERT, S.M.; SWARTHMORE COLLEGE; SWARTHMORE COLLEGE; SWARTHMORE COLLEGE; SWARTHMORE COLLEGE; SWARTHMORE COLLEGE; SWARTHMORE COLLEGE: Recombinant human erythropoietin reduces time to exhaustion during endurance running in Djungarian hamsters, Phodopus sungorus

The glycoprotein hormone erythropoietin (EPO) regulates erythrocyte production, increasing the oxygen-carrying capacity of the blood. Recombinant human EPO (rHuEPO) is used in treatment of anemia but also is abused by endurance athletes with the intention of improving performance. In an effort to determine if EPO causes this performance enhancement in hamsters, we treated a population of Djungarian hamsters (Phodopus sungorus, n = 20) with a 5 IU rHuEPO 0.3 ml injection day-1 or a saline solution for five days. Twelve days after the first injection each hamster was run on a treadmill at 26.8 m/min at a 15% grade until exhausted. The control group required less stimulation in the form of pressurized air puffs to continue running and ran significantly longer before exhaustion (230.6 28.1 min) than did the rHuEPO-injected group (98.5 34.4 min)(P = 0.0185). The combined effects of artificially increased hematocrit and exercise-induced dehydration may have increased blood viscosity in the experimental group resulting in lower performance relative to the control group. We are currently determining whether EPO treatments did indeed increase blood viscosity by measuring hematocrit in hamsters (n = 20) treated with EPO. If EPO increases hematocrit significantly above the levels of the untreated hamsters, then the purported effect of EPO via increased hematocrit is contingent upon a vasculature that can support the increased viscosity and allow for the potential increase in oxygen-carrying capacity. Acknowledging the deaths due to fatally high hematocrit of human professional cyclists who had abused EPO, this study provides insight into the potentially dangerous stresses EPO can haveupon the cardiovascular system.