National Institute of Animal Health (NIAH)

Topics in Animal Health Research 2004

21. Evaluation of bovine serum apolipoprotein E concentration by enzyme-linked immunosorbent assay and characterization of the properties of apolipoprotein E-containing particles


Apolipoprotein E (apoE) is a protein constituent of lipoproteins, and acts as a receptor-binding ligand. We attempted to detect bovine apoE in the plasma of lipoprotein fractions and identified it by determining its N-terminal amino acid sequence. Bovine apoE was purified and an enzyme-linked immunosorbent assay was developed. Using this assay system, the effect of fasting and lactating on the concentration of apoE in bovine plasma was investigated. After the fasting, the concentration of plasma apoE had significantly increased. The apoE concentrations during the lactating stage in cows were significantly higher than during the nonlactating stage. In lactating plasma, apoE eluted in high-density lipoprotein fractions separated by gel filtration increased. These apoE-containing particles contained few lipids. Additionally, bovine primary cultured hepatocytes secrete apoE, and purified apoE-containing particles from bovine hepatocyte medium consist of apoE only. These results suggest that apoE-containing particles, which increased during the lactating stage, were not associated with high-density lipoprotein particles, and that lipid-free forms of apoE were included in the cow plasma.
(Metabolic Disease Section, Department of Production Diseases TEL +81-29-838-7795)


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