Endogenous erythropoietin and salt sensitivity of blood pressure in patients with essential hypertension.

To investigate a possible involvement of endogenous erythropoietin (EPO) in the salt sensitivity of blood pressure in essential hypertensive (EHT) patients, plasma EPO concentrations were measured during different salt intakes in 14 patients with EHT. All patients were given low salt (34 mmol NaCl/day) and high salt (342 mmol NaCl/day) diet of 7 days each. The plasma EPO concentrations were significantly higher on the high salt diet than those of low salt diet (23.5 +/- 1.9 v 18.7 +/- 1.8 mIU/ml, mean +/- SD, P < .05). The percentage change of plasma EPO concentration with salt loading correlated positively with hematocrit (Ht) at high salt diet (r = -0.62, P < .02) and tended to be correlated with plasma hemoglobin at high salt diet (r = 0.52, P < .10). These results suggest that the secretion of EPO is increased in response to hemodilution caused by the salt loading and the increased EPO concentration in plasma which may contribute to the increase in blood pressure through an expansion of total blood volume due to an enhanced red cell generation in combination with salt and water retentions.