INFLUENCE OF WATER IMMERSION ON PLASMA ERYTHROPOIETIN CONCENTRATION IN PATIENTS WITH ESSENTIAL-HYPERTENSION

Water immersion (WI) is followed by hypoxemia and hemodilution. and in duces alterations in renal hemodynamics (increase in tubular sodium lo ad). These facts justified the performance of studies which aimed to a ssess the influence of WI on erythropoietin (EPO) secretion. Serum EPO and atrial natriuretic peptide (ANP) concentrations as well as plasma renin activity (PRA) were estimated in 18 patients with essential hyp ertension (EH) and in 9 healthy subjects (HS): before, after 2 h of WI and 2 h after discontinued WI. WI was followed by a significant incre ase in plasma volume and decrease in PRA, which were of similar magnit ude in both examined groups. Patients with EH showed significantly hig her basal levels of serum EPO (66.7+/-11.4 mU/ml in EH vs. 20.0+/-3.4 mU/ml in HS) and ANP (110.6+/-15.4 pg/ml in EH vs. 75.6+/-8.2 pg/ml in HS). WI was followed by a significant increase in both EPO (by 34.0+/ -8.9 mU/ml in EH and 17.0+/-5.4 mU/ml in HS) and ANP (by 106.9+/-19.2 pg/ml in EH and 149.4+/-16.9 pg/ml in HS). Only in EH, a significant c orrelation was found between serum EPO level and mean arterial pressur e post WI and natriuresis during WI, respectively. Conclusions: (1) wa ter immersion induced increase in plasma EPO both in healthy subjects and patients with essential hypertension. (2) Patients with EH are cha racterized by elevated basal plasma levels of ANP and EPO, (3) Partici pation of the renin-angiotensin system and ANP in the regulation of EP O secretion could not be proven both in normotensive subjects and hype rtensive patients.