Background: Exaggerated erythropoietin (EPO) response to phlebotomy regardless of the baseline EPO levels have been shown in patients with post-transplant erythrocytosis (PTE) and administration of angiotensin-converting enzyme inhibitors (ACE-1) seems to be effective in controlling PTE. However, the mechanism of this ACE-1 induced reduction in haematocrit (Hct) is not well known. Although some authors have suggested that ACE-1 may reduce EPO secretion, this is still controversial. The aim of the present study was to assess the effect of a single dose ACE-1 on exaggerated EPO response to phlebotomy.
Methods: In this study, we compared serum EPO and renin (PRA) levels of 10 PTE patients, 10 non-PTE patients and 10 healthy blood donors before and after phlebotomy. The effects of a single dose of ACE-1 (enalapril, 5 mg p.o.) in PTE patients were also evaluated in the second phlebotomy.
Results: While the mean basal serum EPO level was significantly higher in the PTE group than the other two groups (P<0.01), the mean basal PRA levels did not differ significantly between these groups. Serum EPO and PRA levels increased significantly after the phlebotomy (P<0.001) and exaggerated EPO response to phlebotomy was suppressed by single dose enalapril (P<0.001) in the PTE patients.
Conclusion: The present study has shown that the renin angiotensin system plays an important role in EPO formation and the Hct lowering effect of the ACE-1 is through reduction of EPO in PTE patients.