Evaluation of the stability of human erythropoietin in samples for radioimmunoassay

Erythropoietin treatment of anemia associated with multiple myeloma

Anemia is a common complication of multiple myeloma. It resolves early in the disease if chemotherapy induces a complete remission, but persists if the disease progresses, causing disabling symptoms and often requiring blood transfusions. We treated 13 patients with myeloma-associated anemia by administering recombinant human erythropoietin three times a week for six months. Eleven patients (85 percent) had steady increases in hemoglobin levels and eventual correction of the anemia. Their symptoms of anemia subsided, and they reported a heightened sense of well-being. No patient had any adverse side effects, particularly episodes of hypertension. Monitoring of the serum M component showed a predominantly stable tumor load without apparent interaction between the underlying disease and the response to erythropoietin therapy. The number of erythroid burst-forming units in the bone marrow and peripheral blood and the level of erythropoiesis in bone marrow smears increased significantly during therapy. Pretreatment serum levels of erythropoietin were higher in the patients who did not respond and in those who required more than two months of treatment before they responded. Serum iron, ferritin, and transferrin concentrations reflected responses to treatment. We conclude that recombinant human erythropoietin is a promising therapeutic tool for treating myeloma-associated anemia.

Serum immunoreactive erythropoietin of children in health and disease

Serum immunoreactive erythropoietin (siEPO) was determined in cord serum from neonates (n = 97, gestational age 36-43 weeks), in healthy children from birth to adolescence (n = 260) and in children with haematological (n = 30), renal (n = 10) and congenital heart diseases (n = 70). In healthy children siEPO levels decreased after birth (geometric mean cord siEPO 35.6 mU/ml with 95% range of 17-56 mU/ml in eutrophic, nondistressed fetuses) and reached lowest values during the first 2 months (geometric mean siEPO 11.5 mU/ml). Thereafter siEPO levels increased slightly and were constant between 2 months and adolescence. The geometric mean siEPO for healthy children after birth was 18.8 mU/ml with 95% range of 7-47 mU/ml. These estimates were not significantly different from normal adult values. In newborns with fetal distress (n = 15) cord siEPO was significantly elevated (geometric mean 63.0 mU/ml; P less than 0.001). In children with haematological disease, siEPO and Hb concentration were inversely correlated (log siEPO (mU/ml) = 4.1-0.20 x Hb (g/dl); r = -0.62; P less than 0.0005). This relationship was significantly different in children with chronic renal failure (log siEPO (mU/ml) = 0.67 + 0.035 x Hb (g/dl); r = 0.50; P = 0.1). In children with heart disease the geometric mean siEPO was 19.2 mU/ml with 95% range 8-65 mU/ml for cyanotic (SaO2 less than 94%) and 17.7 mU/ml with 95% range of 12-36 mU/ml for acyanotic patients. In this group siEPO values were inversely correlated to the arterial oxygen content (log siEPO (mU/ml) = 1.61-2.04 x oxygen content (l/l); r = -0.28; P less than 0.02).

Erythropoietin in polycystic kidneys

Erythropoietin (EPO) formation in kidneys of 18 patients with autosomal dominant polycystic kidney disease (ADPKD) was investigated. In 12 patients on hemodialysis and in 6 patients with preterminal renal failure serum, EPO was 29 +/- 7 and 16 +/- 1.5 mU/ml and hemoglobin concentrations were 11.0 +/- 0.6 and 12.7 +/- 1.2 g/dl, respectively. Cyst fluid from a total of 357 renal cysts was obtained by either in vivo aspiration or immediately after nephrectomy. The cysts contained variable concentrations of bioactive EPO from undectable values up to 3.2 U/ml. A pronounced enrichment of EPO was observed in cysts with sodium concentrations greater than 100 mmol/liter, suggesting an association with proximal tubular malformations. The EPO concentrations in the cysts were neither correlated with the protein concentration nor with the oxygen pressure of the cyst fluid. Using a cDNA probe for human EPO, mRNA for EPO was localized in stroma cells of the cyst walls by an in situ hybridization technique. Our findings suggest that single interstitial cells juxtaposed to proximal tubular cysts may produce EPO independent of the oxygen pressure inside the cysts, which ameliorates the anemia during end-stage polycystic kidney disease.

Pharmacokinetics of recombinant human erythropoietin in patients on continuous ambulatory peritoneal dialysis

To determine the optimum regimen for giving recombinant human erythropoietin (EPO) to patients on continuous ambulatory peritoneal dialysis (CAPD), the pharmacokinetics of single-dose EPO administered intravenously (120 U/kg), intraperitoneally (50,000 U), and subcutaneously (120 U/kg) was investigated. After intravenous administration serum EPO levels decayed exponentially from a peak of 3959 mU/ml, with a half-life of 8.2 h. 2.3% of the total intravenous dose was lost in the dialysate during the first 24 h. Peak serum EPO levels of 375 mU/ml at 12 h and 176 mU/ml at 18 h were attained following intraperitoneal and subcutaneous administration, respectively. The bioavailability of subcutaneous EPO (21.5%) was seven times greater than that of intraperitoneal EPO (2.9%). These results suggest that subcutaneous EPO represents the most satisfactory route of administration for CAPD patients.