SUPPRESSION OF THE RENIN-ANGIOTENSIN ALDOSTERONE AXIS WITH ERYTHROPOIETIN THERAPY BY A NEGATIVE FEEDBACK LOOP

To investigate the pathophysiology of hypertension in patients receivi ng recombinant human erythropoietin (rHuEpo) we studied its effects on the renin-aldosterone axis of chronic haemodialysis (HD) patients not receiving antihypertensive drugs. Nine severely anaemic normotensive HD patients received rHuEpo 50 U/kg bodyweight, thrice weekly after ea ch HD. The dose was increased by 25 U/kg bodyweight every 4 weeks to a maximum of 100 U/kg or until an increase of Hb or Hct of 2 g/dl or 7% was achieved. Blood samples were taken after 30 min supine rest and w hile seated 10 min later after gentle ambulation. Results expressed as mean +/- SEM: [GRAPHICS] Both parameters decreased in all patients du ring rHuEpo therapy, but there were no changes in mean arterial pressu re (89 +/- 5 versus 89 +/- 5 mmHg) or body-weight (62 +/- 5 versus 62 +/- 5 kg). Haemoglobin (g/dl) and haematocrit (%) increased from 6.2 /- 0.6 and 19.1 +/- 0.8 to 8.2 +/- 1.3 and 24.5 +/- 1.14 respectively (P < 0.01). We therefore conclude that suppression of the renin-aldost erone axis occurs during rHuEpo therapy in normotensive HD patients by a negative feedback loop, before the development of hypertension.