NO ACUTE CHANGE OF SERUM ERYTHROPOIETIN IN RESPONSE TO HYPOCALCEMIA OR ANTIHYPERTENSIVE AGENTS IN UREMIC PATIENTS

Endogenous erythropoietin (EPO) secretion can still be modulated in pa tients with end-stage renal failure but only in response to strong sti muli. Thus even anephric dialysis patients are able to increase EPO pr oduction acutely when exposed to a marked hypoxic stimulus. The presen t study was designed to test the hypothesis that a decrease of plasma calcium or the administration of various antihypertensive agents might be able to induce acute changes of plasma EPO concentration. Four gro ups of chronic hemodialysis patients were studied. Eight patients volu nteered for the induction of an acute, transient hypocalcemia via a ca lcium-free dialysate during the initial 60 min of a regular dialysis s ession of 240 min. Plasma immunoreactive (i) EPO, total calcium, and i ntact parathyroid hormone (iPTH(1-84)), as well as blood ionized calci um and blood gases were measured before as well as 30, 60, 120 and 240 min after the start of dialysis. In addition, plasma iEPO was measure d 48 h after the session. Patients of group 2 (n = 6), group 3 (n = 6) , and group 4 (n = 7) received the day after a hemodialysis session a single dose of either acetazolamide, furosemide, or enalapril, respect ively, and their plasma iEPO was determined before and 3, 6 and/or 24 h after drug administration. In group 1, plasma total calcium decrease d from 2.39 +/- 0.07 mM (mean +/- SEM) to 1.98 +/- 0.02 and 1.83 +/- 0 .03 mM after 30 and 60 min of dialysis, respectively, and blood ionize d calcium from 1.28 +/- 0.04 to 1.02 +/- 0.03 and 0.92 +/- 0.04 mM, re spectively. Circulating iPTH rose from a basal value of 96 +/- 27 pg/m l to 431 +/- 154 and 374 +/- 156 pg/ml at 30 and 60 min, respectively. Plasma iEPO levels were however unchanged during the 60 min of calciu m-free dialysis and thereafter (21.8 +/- 1.2 vs. 21.8 +/- 1.3 mU/ml at 0 and 60 min, respectively), as were blood gases and pH. After the ad ministration of hypertensive agents, there was also no acute change of plasma iEPO except for furosemide (group 3) where a borderline decrea se of plasma iEPO was observed after 6 h (from initially 51.6 +/- 11.6 to 31.4 +/- 4.3 mU/ml, p < 0.06). In conclusion, neither the inductio n of hypocalcemia nor the administration of antihypertensive agents le ad to acute changes of plasma iEPO levels in chronic hemodialysis pati ents.