Treatment with rhEpo increases transferrin receptor (TfR1) expression in skeletal muscle. The figure shows the changes in TfR1 expression in muscle biopsy samples obtained from the vastus lateralis before and after 8 and 28 days of rhEpo treatment. (A) TfR1 mRNA levels were normalized to total cDNA content and are expressed in relation to the pretreatment value, arbitrarily defined as 100. (B) Equal amounts of proteins (as assessed by amido black staining) from the muscle biopsy extracts were loaded onto SDS polyacrylamide gels, immunoblotted with antibodies against TfR1, and visualized by chemiluminescence. The result shown is representative of 3 independent experiments obtained with extracts from 2 participants (#1 and #2). (C) The densitometric quantification of the immunoblot analysis of TfR1 protein content before and after 8 and 28 days of rhEpo treatment. Values are mean ± SE for 8 participants. The statistical differences from pre-rhEpo values were calculated with the Wilcoxon test; *P < .05.