In situ hybridization was used to quantitate the cells that produce erythropoietin (EP) in the renal cortices of mice with varying severities of acute anemia and of mice recovering from severe, acute anemia. The number of EP-producing cells in the renal cortex increased in an exponential manner as hematocrit was decreased. Individual EP- producing cells had very similar densities of silver grains in autoradiograms regardless of whether they were from normal mice or from slightly, moderately or severely anemic animals. With increasingly severe anemia, total renal EP mRNA levels and serum EP concentrations showed increases that correlated with the number of renal EP-producing cells. These results indicate that as mice become more anemic, additional cells are recruited to produce EP rather than the cells already producing EP being stimulated to increase their individual production. In mildly and moderately anemic animals, small clusters of EP-producing cells were found in the inner cortex with large areas of cortex containing no EP-producing cells. In severely anemic mice, EP- producing cells were found throughout the inner cortex with only a very few found scattered in the outer cortex and outer medulla. The data indicate that only a subset of total renal interstitial cells produce EP. During recovery from severe, acute anemia, the numbers of EP- producing cells decreased exponentially as hematocrits rose and correlated with decreases in total renal EP mRNA and serum EP concentrations. These results suggest that following an acute blood loss and during the recovery from a blood loss, the capacity to deliver oxygen, as represented by hematocrit, is the major regulator of EP production.
The concentration of human marrow progenitors CFU-E, BFU-E, CFU-GM, and CFU-Mk and the percentage of these progenitor cells in DNA synthesis were studied in nine patients with transfusion-dependent anemia of end- stage renal failure before and 2 weeks after treatment with human recombinant erythropoietin (Epo) at a dose of 150 to 300 U/kg intravenously three times per week. The concentration of CFU-E in the posttreatment marrow increased by a mean of 4.15-fold, BFU-E by 3.37- fold, CFU-GM by 1.86-fold, and CFU-Mk by 1.96-fold as compared with their respective concentrations in the pretreatment marrows. This increase in the concentrations of marrow progenitors was accompanied by almost a doubling of the percentage of these cells in DNA synthesis as assessed by the 3H-thymidine suicide technique. These observations demonstrate that at the progenitor cell level the human marrow responds to therapeutic doses of Epo as an organ rather than by a selective expansion of the erythroid cell line.
Twenty-seven patients receiving a standard cytosine arabinoside and daunorubicin regimen as induction of reinduction therapy of acute myelogenous leukemia were randomly assigned to receive lithium carbonate, 300 mg t.i.d., or no lithium. Treatment groups were comparable with respect to age and baseline granulocyte counts. All patients developed granulocyte nadirs below 100/cu mm. By actuarial analysis, the median duration of granulocytopenia, less than 1000/cu mm, was 16.0 days in the lithium group and 24.6 days in the no-lithium group, p = 0.013. The median duration of granulocytes less than 500/cu mm also favored the lithium group but only approached statistical significance: 14.0 days versus 20.5 days, p = 0.054. Lithium levels between 0.5 and 1.0 meq/liter were easily maintained in 11 of 12 patients receiving lithium, 300 mg t.i.d., and toxicity directly attributable to lithium was not observed. Despite the shortened duration of neutropenia, the incidence of infections and the rate of remission were not affected.
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