Erythropoietin does not affect nitric oxide system in rats with chronic renal failure

We investigated to see whether an altered role of nitric oxide (NO) system is involved in erythropoietin (EPO)-induced hypertension in chronic renal f ailure (CRF). Male Sprague-Dawley rats were five-sixths nephrectomized to i nduce CRF. Six weeks after the operation, EPO or Vehicle was injected for a nother 6 weeks. Plasma and urine nitrite/nitrate (NOx) levels were determin ed. Expression of NO synthase (NOS) proteins in the aortae and kidneys were also determined. In addition, the isometric tension of isolated aorta in r esponse to acetylcholine and nitroprusside was examined. Blood pressure pro gressively rose in CRF groups, the degree of which was augmented by EPO tre atment. Plasma NOx levels did not differ among the groups, while urine NOx levels were lower in CRF groups. Endothelial NOS expression was lower in th e kidney and aorta in CRF rats, which was not further affected by EPO-treat ment The inducible NOS expression in the kidney and aorta was not different among the groups. Acetylcholine and sodium nitroprusside caused dose-depen dent relaxations of aortic rings, the degree of which was not altered by EP O-treatment. Taken together, EPO-treatment aggravates hypertension in CRF, but altered role of NO system may not be involved.