Effect of rhEPO administration on serum levels of sTfR and cycling performance.
OBJECTIVE
We assessed the possibility of using soluble transferrin receptor (sTfR) as an indicator of doping with recombinant erythropoietin (rhEPO).


METHODS
A double-blind, placebo-controlled study was conducted with the administration of 5,000 U of rhEPO (N = 10) or placebo (N = 10) three times weekly (181-232 U x kg(-1) x wk-1) for 4 wk to male athletes. We measured hematocrit and the concentration of hemoglobin, sTfR, ferritin, EPO, and quantified the effects on performance by measuring time to exhaustion and maximal oxygen uptake (VO2max) on a cycle ergometer.


RESULTS
Hematocrit increased from 42.7 +/- 1.6% to 50.8 +/- 2.0% in the EPO group, and peaked 1 d after treatment was stopped. In the EPO group, there was an increase in sTfR (from 3.1 +/- 0.9 to 6.3 +/- 2.3 mg x L(-1) , P < 0.001) and in the ratio between sTfR and ferritin (sTfR-ferritin(-1)) (from 3.2 +/- 1.6 to 11.8 +/- 5.1, P < 0.001). The sTfR increase was significant after 1 wk of treatment and remained so for 1 wk posttreatment. Individual values for sTfR throughout the study period showed that 8 of 10 subjects receiving rhEPO, but none receiving placebo, had sTfR levels that exceeded the 95% confidence interval for all subjects at baseline (= 4.6 mg x L(-1)). VO2max increased from 63.6 +/- 4.5 mL x kg(-1) x min(-1) before to 68.1 +/- 5.4 mL x kg(-1) x min(-1) 2 d post rhEPO administration (7% increase, P = 0.001) in the EPO group. Hematocrit, sTfR, sTfR-ferritin(-1), and VO2max did not change in the placebo group.


CONCLUSIONS
Serum levels of sTfR may be used as an indirect marker of supranormal erythropoiesis up to 1 wk after the administration of rhEPO, but the effects on endurance performance outlast the increase in sTfR.
Hormone Laboratory, Aker University Hospital and Norwegian University of Sport and Physical Education, Oslo. kare.birkeland@ioks.uio.no
K I
KI
Birkeland
J
J
Stray-Gundersen
P
P
Hemmersbach
J
J
Hallen
E
E
Haug
R
R
Bahr
D000328:Adult; D001642:Bicycling / Q000502:physiology*; D004311:Double-Blind Method; D004920:Erythropoiesis / Q000187:drug effects / Q000502:physiology; D004921:Erythropoietin / Q000008:administration & dosage / Q000494:pharmacology*; D005293:Ferritins / Q000097:blood; D006400:Hematocrit; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D010807:Physical Endurance; D011994:Recombinant Proteins
D011994:Recombinant Proteins; D004921:Erythropoietin; D005293:Ferritins