Currently, erythropoietin (EPO) treatment in anemic patients is getting more interest, but in long term, development of hypertension is common problem in EPO treated patients. Since it isn't yet known whether EPO affects directly vascular and/or kidney functions, we aimed to study effects of acute EPO treatment on renal tissue nitrite level, and cardiovascular function and glomerular filtration rate (GFR). Experiments were done under 4 groups. Group I: Sham operated control, group II: 150 IU/kg EPO, group III: 50 mg/kg Nw-nitro-L-arginine methyl ester (L-NAME), group IV: L-NAME+EPO. Femoral artery, vein and bladder were catheterized under anesthesia. After stabilization and first 45 min basal control period, drugs were given i.v. bolus infusion according to the group protocols, then 2 x 45 min clearance periods were followed. EPO infusion increased renal tissue nitrite activity causing GFR increase without any influence on systemic blood pressure. L-NAME alone or together with EPO significantly raised the systemic blood pressure with a partial increase in GFR, but L-NAME treatment significantly reduced tissue nitrite level. The present study for the first time suggests that exogenous EPO treatment increases rat GFR and renal tissue nitrite level without affecting systemic blood pressure.