Résumé
BACKGROUND: Thrombopoietin (TPO) is a major cytokine which plays a critical role in the regulation of thrombopoiesis and megakaryopoiesis. Since the kidney is one of the TPO-producing organs, it is hypothesized that TPO deficiency in end stage renal disease can give rise to thrombocytopenia. However, serum TPO levels and their clinical significance in maintenance hemodialysis patients with thrombocytopenia are not completely evaluated. The aim of the present study was to compare the percentage of reticulated platelets and serum TPO levels between non-thrombocytopenic group (platelet count > or =150x109/L, non-T group) and thrombocytopenic group (platelet count <150x109/L, T group) and to investigate the local and/or systemic effect of the TPO on the platelet count in hemodialysis patients. METHODS: We measured the percentage of reticulated platelets and serum TPO levels in samples obtained from venous returns of arteriovenous fistula (AVF) and contralateral peripheral veins in 44 hemodialysis patients. Serum reticulated platelets were measured by flow cytometry and serum TPO levels were determined with a commercially available ELISA kit. Patients with a history of HBV/HCV infection and hepatobiliary disease were excluded. RESULTS: Reticulated platelets of T group (4.57+/-2.32%) were significantly lower than non-T group (7.79+/-3.62%) (p<0.05). Serum TPO levels obtained from venous return of AVF in T group (78.37+/-15.48 pg/mL) were lower than non-T group (98.15+/-35.05 pg/mL) (p<0.05). Serum TPO levels obtained from contralateral peripheral veins in T group (77.20+/-17.28 pg/mL) were lower than non-T group (104.73+/-38.45 pg/mL) (p<0.01). There were no statistically significant difference of serum TPO levels between venous return of AVF and contralateral peripheral veins in T group. CONCLUSION: Decreased circulating reticulated platelets and serum TPO levels despite low platelet counts in comparison with normal platelet counts in hemodialysis patients, suggesting that the feedback mechanism, the TPO producing organ and bone marrow is not working with effect in the regulation of thrombopoiesis. An alteration in the production and regulation of TPO level is not influenced by local factor like an AVF endothelium.