Regulation of erythropoiesis. 18. The effect of vincristine and erythropoietin on bone marrow.

Abstract

results to be reported herein appear to favor different immediate precursors and a more primitive pluripotential precursor cell. MethodsAdult female Sprague-Dawley rats weighing 150 to 170 g were given vincristine in a single intravenous dose of 0.3 mg per kg. This dose is just below the lethal range in this colony; 0.4 mg per kg resulted in a 90% mortality within 10 days. Rats, when transfused, were given washed, packed homologous red cells by tail vein injection 5 days before the start of the experiment. They received red cells in an amount equivalent to 3.5%o of the body weight. One hundred units of human urinary erythropoietin, prepared by alcohol fractionation (4), was given by subcutaneous injection. Blood samples were collected by cardiac puncture from anesthetized animals into Versenate. Peripheral blood values were measured by standard technics. Leukocyte differential counts were based on the evaluation of 200 cells in peripheral smears. Bone marrow smears were made from the split femur by a brush technic. The percentage of erythroid precursors was estimated from differential counts on 500 to 1,000 nucleated cells. The mitotic index was measured in these same preparations. Megakaryocytic differentials were based on evaluation of 100 megakaryocytes. Blood volume was measured from the dilution of intravenously administered 'Cr-labeled washed homologous red cells. Blood samples for red cell wFe incorporation were collected 20 hours after intravenous administration of plasmabound 'Fe. They were lysed with saponin and counted in a well type scintillation counter. The total iron incorporation was based on direct measurement of the blood volume. ResultsAfter the administration of vincristine to normal animals, the marrow smears revealed an accumulation of metaphase forms that approximated linearity for the first 4 hours. Extrapolation of this curve to 100% provided an estimate of -11 hours for the generation time of rat erythroid precursors. By 8 hours, 67% of erythroid precursors potentially capable of dividing and 23%o of granulocytic precursors potentially capable of dividing were in metaphase. No postmetaphase forms were 1241

A Comparison of the Three <i>in vivo</i> Assays for Haemopoietic Stem Cells

“…With the exception of the GRA curve after ni trogen mustard (see above), the shapes of the dose response curves for the 3 assays are as expected for three different cell populations proliferat ing at different rates [5]. These results, therefore, favour the existence of different populations of stem cells, and would be consistent with the con siderable amount of evidence from other types of investigation [1,2,7,8,17,18] which have suggested the existence of different populations of re populating cells committed to separate lines of haemopoietic differentia tion. The present studies with proliferation-dependent cytotoxic agents then lead to the conclusion that the erythroid repopulating cells prolifer ate rather more quickly, and the granulocytic repopulating cells, some what unexpectedly, more slowly than the CFU.…”

Effects of Erythropoietin on Glucose Metabolism

“…While acute treatment with EPO had no eff ect on glucose metabolism, sustained administration of EPO improved glucose utilization by reducing insulin resistance [ 16 ] . The observations of Bianchi et al [ 17 ] indicated that Introduction ▼ The glycoprotein hormone erythropoietin (EPO) was fi rst identifi ed as the key regulator of red blood cell diff erentiation and maturation in 1966 [ 1 ] . EPO is synthesized by the kidney peritubular interstitial cells; typically, the lack of EPO production associated with chronic kidney disease results in hypoproliferative anemia.…”

Effect of Erythropoietin on Early Recovery of Erythropoiesis in Mice after Sublethal Dose of 5-Fluorouracil

“…An enhancing effect of erythropoictin upon erythroid regeneration has been reported in sublethally radiated animals (5) and after vincristine injection in polycythemic rats (6). In the latter study, Morse and Stohlman noticed a delayed response to erythropoietin and considered as an explanation a continued availability of the injected erythropoietin or a storage of information imparted by it.…”

“…I t has remained undecided whether the latter represents an intermediate stage (6) or whether it is identical with the primitive and perhaps pluripotential stem cell. Erythropoietin unquestionably induces transformation of the immediate precursor into a proerythroblast, and there is also evidence of its enhancing action on later stages of erythroid cells.…”