Effect of erythropoietin on renal excretion of a sodium load

To determine whether erythropoietin alters the renal excretion of a sodium load in humans, we administered either erythropoietin (150 units/kg) or vehicle intravenously in a randomized crossover design to six normal white men on day 4 of a controlled sodium diet. After erythropoietin administration, the subjects were given 2 L normal saline solution intravenously over 4 hours. All urine was collected for 4 days after drug administration. Serum sodium and creatinine levels and blood pressure were determined 0, 4, 8, and 24 hours after drug administration. Peripheral renin activity and aldosterone levels were determined 0, 4, and 8 hours after drug administration. Erythropoietin significantly decreased total sodium excretion during the 4 days after drug administration (erythropoietin = 784 +/- 46 mEq/4 days versus control = 840 +/- 41 mEq/4 days; p < 0.001). Erythropoietin did not alter creatinine clearance, blood pressure, or the changes in plasma renin activity and aldosterone caused by the saline load. We conclude that erythropoietin decreases urine sodium excretion after a sodium load in normal human subjects without altering glomerular filtration rate, blood pressure, or plasma renin activity.