Erythropoietin in patients with essential hypertension

The role of erythropoietin (EPO) in the etiopathogenesis of essential hypertension (EH) has not yet been fully established. It is known that EPO activates the tissue renin-angiotensin system and synthesis of endothelin and serotonin, exerts direct vasopressor effects and diminishes the effects of nitric oxide on the vascular smooth muscles.

To establish whether endogenous EPO is a pathogenic factor in the development of EH.

The study group consisted of 74 patients aged 17-79 years (mean age 54+/-15 years) with EH. The control group consisted of 11 healthy volunteers (4 women and 7 men, aged 20-71 years). Mild EH (MiEH) was detected in 20 patients, moderate EH (MdEH) in 34 patients and severe EH patients (SEH) in 20 patients. The patients were also divided into 3 groups according to the severity of organ damage (by WHO standards); 1st degree organ damage (DOD) was observed in 13 patients, 2nd DOD - in 49 patients, and 3rd DOD - in 12 patients. EPO serum concentration was determined by a radioimmunological method. We also evaluated echocardiographic parameters, renin plasma activity, serum concentration of aldosterone, hematocrit, red blood cell count, creatinine and potassium serum concentrations, creatinine clearance and 24-hour urine microalbuminuria.

The baseline EPO serum concentration was significantly higher in patients with SEH than in the control group (11.8+/-7.0 vs 6.9+/-4.3 ng/ml, p<0.05) and in patients with 3rd DOD compared with controls (12.5+/-8.9 vs 6.9+/-4.3 ng/ml, p<0.05). There were no statistically significant differences in baseline EPO serum concentration between patients with MiEH, MdEH, 1st and 2nd DOD and control group. In patients with MiEH, EPO correlated positively with the interventricular septum diameter (r=0.519). In patients with MdEH and in patients with 2nd DOD, EPO correlated positively with renin plasma activity (r=0.424 and r=0.288, respectively). In patients with SEH, EPO correlated positively with potassium concentration and 24-hour microalbuminuria (r=0.574 and r=0.465, respectively). EPO correlated negatively with creatinine concentration (r=-0.768) and positively with creatinine clearance (r=0.769) in patients with 1st DOD. In patients with 2nd DOD, EPO correlated negatively with end-systolic left ventricular diameter (r=-0.291).

We observed a significant elevation of EPO serum concentration in patients with SEH and 3rd degree organ damage. EPO correlated also with different neurohumoral, biochemical and echocardiographic parameters. These findings suggest that EPO may contribute to the development of essential hypertension but this hypothesis needs to be tested in further studies.