Erythroid progenitor cell assays and serum erythropo1etin levels in uremic patients with erythrocytosis

We studied the in vitro erythroid progenitor (BFU-E) growth, serum erythropoietin (EPO) levels, and the effect of urémie sera on normal erythropoiesis in 12 patients with chronic renal failure and erythrocytosis. All patients required maintenance dialysis. They all had a hematocrit > 50% and an arterial oxygen saturation > 95%. Four patients fulfilled the diagnostic criteria for polycythemia vera (PV, group A), 4 had acquired cystic disease of the kidney (group B), and the remaining 4 had erythrocytosis of unknown causes (group C). The numbers of EPO-dependent BFUE in marrow and blood of the urémie patients were normal or increased as compared with normal controls. EPO-independent erythroid colonies were present in alt 4 patients of group A and were absent in groups B and C. The serum EPO levels, measured by radioimmunoassay, were variable: 3 low and 1 normal in group A; 1 normal and 3 increased in group B; 3 normal and I elevated in group C, There was no correlation between serum EPO levels and hematocrit values. In the absence of exogenous EPO, when urémie serum in group A or B was added to normal marrow cultures, no erythroid colony was found; whereas sera of 2 patients in group C could stimulate normal marrow to form BFU-E colonies. In the presence of exogenous EPO, with the addition of each urémie serum, the normal marrow gave rise to BFU-E colonies ranging from 80% to 160% of those with the addition of normal serum. The present study showed that (1) urémie patients with erythrocytosis had normal or increased BFU-E numbers, (2) PV with renal failure retained the characteristic autonomous erythroid proliferation, (3) urémie sera had no inhibiting effect on normal erythropoiesis and some sera had an erythropoietic activity.