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A hemolytic lipoprotein containing lysophosphatidylcholine produced in incubated mouse plasma
Abstract:
A factor capable of lysing erythrocytes arose in the plasma of various strains of mice when the plasma was incubated at 37 degrees C. The hemolytic activity and the amount of lysophosphatidylcholine (lysoPC) in the plasma reached a maximum at 3 h of incubation. Both the hemolytic activity and the increment portion of lysoPC were recovered from the prealbumin fraction on agarose gel electrophoresis. Serum albumin, an inhibitor of the hemolytic action of lysoPC, inhibited the hemolytic action of the this factor. These and other results indicate that the hemolytic factor is a lipoprotein that contains lysoPC as an active site. The molecular weight of active fraction was distributed from 100 000 to 200 000. The finally purified fraction contained 65% protein composed of a polypeptide with a molecular weight of 25 000. The lipid composition of this fraction was 12.4% lysoPC, 63.9% phosphatidylcholine (PC), 5.4% sphingomyelin, 2.1% triacylglycerols and 16.2% cholesterol. This hemolytic lipoprotein was also found in the prealbumin fraction when electrophoresis of plasma of the lysoPC-administered mice was carried out. However, such lipoprotein was not formed by simple addition of lysoPC to the nonincubated plasma.
Insights
A novel hemolytic factor, a lipoprotein containing lysophosphatidylcholine (lysoPC), was identified in mouse plasma after incubation. This factor, found in the prealbumin fraction, demonstrates erythrocyte-lysing activity.
Area of Science:
- Biochemistry
- Hematology
- Lipidology
Background:
- Erythrocyte lysis can be triggered by various plasma factors.
- Lysophosphatidylcholine (lysoPC) is a known hemolytic agent.
- The formation and nature of endogenous hemolytic factors in plasma require further elucidation.
Purpose of the Study:
- To identify and characterize a novel erythrocyte-lysing factor in mouse plasma.
- To investigate the composition and properties of this hemolytic factor.
- To determine the role of lysophosphatidylcholine (lysoPC) in the formation of this factor.
Main Methods:
- Incubation of mouse plasma at 37°C to induce hemolytic activity.
- Agarose gel electrophoresis to isolate and analyze plasma fractions.
- Characterization of the purified hemolytic factor's protein and lipid composition.
- Assessment of inhibition by serum albumin.
Main Results:
- A hemolytic factor, maximal at 3h incubation, was detected in mouse plasma.
- The factor co-migrated with lysophosphatidylcholine (lysoPC) in the prealbumin fraction.
- The purified factor is a lipoprotein (MW 100,000–200,000) containing lysoPC (12.4%) and protein (65%, MW 25,000).
- Serum albumin inhibited the factor's hemolytic activity.
Conclusions:
- The identified hemolytic factor is a lipoprotein with lysophosphatidylcholine (lysoPC) as its active component.
- This lipoprotein is formed endogenously in plasma upon incubation, not by simple lysoPC addition.
- The findings provide insights into lipid-mediated erythrocyte lysis mechanisms.