CIRCULATING TRANSFERRIN RECEPTOR DURING ERYTHROPOIETIN MEDICATION OF ANEMIC PATIENTS WITH RHEUMATOID-ARTHRITIS

Serum levels of the transferrin receptor (TfR) were monitored in 12 an emic patients with rheumatoid arthritis (RA) undergoing treatment with recombinant human erythropoietin (rHuEPO) for a 24-week period. Measu rement of TfR was performed using an enzyme immunoassay. Compared to a mean pretreatment level of 4.2 mg/l (range 2.1-6.1 mg/l), there was a n increase in the mean TfR concentrations from 2 weeks of treatment on wards to a maximum of 7.7 mg/l (range 2.1-12.3 mg/l) at 12 weeks (p<0. 01). Nine of the 12 patients responded to rHuEPO with an increase in b lood hemoglobin concentration of 1.5 g/l or more. An increase in TfR l evels was documented not only in the responders but also in the 3 nonr esponders. We conclude that in anemic RA patients exogenous erythropoi etin induces a swift and sustained increase in the serum concentration of TfR, which probably reflects increased expression of TfR on erythr oblasts. This sustained elevation of TfR seems to occur even in patien ts who do not have an increase in their hemoglobin level.