IS ENDOGENOUS ERYTHROPOIETIN A PATHOGENETIC FACTOR IN THE DEVELOPMENTOF ESSENTIAL-HYPERTENSION

Background. Recent experimental studies have found that erythropoietin elicits vasoconstriction and proliferation of endothelial cells. We c onducted the following study to assess the possible interactions betwe en endogenous erythropoietin, systemic and renal haemodynamics at diff erent stages of essential hypertension. Methods. We examined 47 patien ts with borderline essential hypertension (age 26+/-3 years) and 49 pa tients with established essential hypertension WHO stage I-II (age 52/-10 years), and compared them to 42 normotensive individuals (age 26/-3 years). The concentration of erythropoietin (radioimmunoassay), 24 -h ambulatory blood pressure (Spacelab 90207), systemic haemodynamics (Doppler sonography) and renal haemodynamics (para-aminohippuric acid and inulin clearance) were determined. Results. Erythropoietin was wit hin normal range and similar among the three groups. In patients with established essential hypertension, a close correlation was found betw een erythropoietin and systolic (r=0.45, P<0.002) and diastolic (r=0.5 1, P<0.001) ambulatory blood pressure. In contrast, ambulatory blood p ressure was not correlated with erythropoietin in subjects with border line hypertension. Total peripheral resistance (r=0.41, P<0.02) was li nked to erythropoietin in established but not in borderline hypertensi on. However, erythropoietin was inversely correlated with renal plasma flow in both established and borderline hypertension (r=-0.33, P<0.05 , and r=-0.34, P<0.05 respectively). In normotensive subjects, in cont rast, erythropoietin was not correlated with any of the determined var iables. In neither group erythropoietin was linked to the haematocrit or hemoglobin concentration. Conclusion. The correlation between eryth ropoietin and renal vascular changes which is already present in borde rline hypertension and is confirmed in established hypertension indica tes an involvement of erythropoietin in the development of essential h ypertension. The presence of normal concentrations of endogenous eryth ropoietin in all groups suggests a dysregulation of erythropoietin in patients with essential hypertension as the pathophysiological link be tween erythropoietin and vascular changes.