1. Elevation of blood pressure is one of the major side effects of recombinant human erythropoietin therapy in haemodialysis patients.
2. We investigated the possible involvement of endothelin in the pathogenesis of this recombinant human erythropoietin-induced blood pressure elevation in 51 patients undergoing maintenance haemodialysis.
3. Blood haemoglobin level increased from 7.1 ± 0.1 to 8.8 ± 0.1g/dl (means ± SEM) after 8 weeks of treatment with recombinant human erythropoietin (3000–4500 units/week). An increase in mean blood pressure was found in 19 patients (37%) (n = 9, by 0–10 mmHg; n = 10, by > 10 mmHg).
4. Plasma immunoreactive-endothelin concentration significantly increased from 2.26 ± 0.18 to 3.14 ± 0.31 pmol/l in the 10 patients whose mean blood pressure increased by more than 10 mmHg (P < 0.05), but not in the other patients. Moreover, the increase in plasma immunoreactive-endothelin concentration showed a significant positive correlation with the change in mean blood pressure in 19 patients with elevated mean blood pressure (r = 0.47, P < 0.05).
5. There was no significant correlation between the change in plasma immunoreactive-endothelin concentration and the change in blood haemoglobin level or the change in body weight.
6. These results suggest the possibility that endothelin may contribute to the recombinant human erythropoietin-related rise in blood pressure in some haemodialysis patients.