Characterization of murine erythropoietin
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Abstract:
Although erythropoietins from human and sheep sources have been purified, a mouse erythropoietin remains essentially uncharacterized despite the fact that the mouse is most commonly used to assay for erythropoietin. Because other murine growth factors may have erythropoietic activity it will be essential to compare these with erythropoietin from murine sources rather than from other species. Here we compare the physicochemical properties and some of the bioactivities of erythropoietins from anemic mouse serum and human urine in parallel fractionations. Both molecules showed similar molecular weights (40-45,000) by gel filtration and similar retention characteristics on reverse-phase high-performance columns. However, they differed in their relative solubility in ammonium sulfate, hydrophobicity on phenyl-Sepharose, and in their ability to bind to a phenyl-boronate agarose column. Despite these differences the two molecules stimulated the same number of CFU-E in the mouse fetal liver assay and did so with similar dose-response relationships. The data indicate that putative murine erythropoietic stimuli must be compared with murine erythropoietin and not human urine erythropoietin before concluding, on the basis of fractionation results, that a factor is different from erythropoietin.
Insights
Murine erythropoietin (EPO) was compared to human EPO. Despite differing physicochemical properties, both stimulated similar red blood cell production in mice, highlighting the need for species-specific comparisons.
Area of Science:
- Biochemistry
- Hematology
- Molecular Biology
Background:
- Erythropoietins (EPO) from human and sheep sources are purified, but mouse EPO remains uncharacterized.
- Mice are crucial for erythropoietin assays, necessitating characterization of murine EPO.
- Other mouse growth factors may possess erythropoietic activity, requiring comparison with murine EPO.
Purpose of the Study:
- To compare the physicochemical properties and bioactivities of erythropoietins from anemic mouse serum and human urine.
- To establish a basis for distinguishing murine erythropoietic factors from EPO.
Main Methods:
- Parallel fractionation of erythropoietins from anemic mouse serum and human urine.
- Analysis of molecular weight using gel filtration.
- Assessment of retention on reverse-phase high-performance liquid chromatography (RP-HPLC) columns.
- Evaluation of solubility in ammonium sulfate.
- Determination of hydrophobicity on phenyl-Sepharose.
- Binding assays using phenyl-boronate agarose columns.
- Bioactivity assessment using the mouse fetal liver assay for CFU-E stimulation.
Main Results:
- Both mouse and human EPO exhibited similar molecular weights (40-45,000 Da) via gel filtration.
- Similar retention times were observed on RP-HPLC columns for both molecules.
- Differences were noted in solubility, hydrophobicity, and binding affinity to phenyl-boronate agarose.
- Despite physicochemical differences, both molecules stimulated comparable numbers of CFU-E in the mouse fetal liver assay with similar dose-response curves.
Conclusions:
- Murine erythropoietin and human erythropoietin share functional similarities in stimulating erythropoiesis in mice.
- Physicochemical differences between mouse and human EPO exist, impacting their isolation and characterization.
- It is essential to compare potential murine erythropoietic stimuli with murine EPO, not human EPO, to avoid misidentification.