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Apoprotein A-I measured by radial immunodiffusion in heparin-MnCl2 supernates
Abstract:
We compared measurements of apoprotein A-I (apoA-I) in plasma and in heparin-MnCl2 supernates analyzed by radial immunodiffusion. The apoA-I values were similar when the samples were fresh [n = 41, mean (SD), mg/L: plasma, 1393.4(349); heparin-MnCl2 supernates, 1364.9(332), p less than 0.01], but were greater than 8% lower in heparin-MnCl2 supernates after storage for seven days at 4 degrees C [plasma, 1348.0(351); heparin-MnCl2 supernates, 1237.6(342), p less than 0.001]. Neither heparin nor MnCl2 interfered directly with the immunodiffusion assay, and treating samples with tetramethylurea and urea to maximize the exposure of apoA-I did not prevent the decrease. MnCl2 (46 mmol/L) added to isolated HDL (d 1.063-1.21) decreased apoA-I values by 5.6% when measured immediately and by 16.7% after storage at 4 degrees C for seven days. High-density lipoprotein cholesterol values were unchanged by MnCl2. The results indicated that apoA-I was more stable in plasma than in heparin-MnCl2 supernates, probably because of an interaction between apoA-I and MnCl2.
Insights
Apolipoprotein A-I (apoA-I) is less stable in heparin-MnCl2 supernates than in plasma, especially after storage. This suggests a potential interaction between apoA-I and MnCl2, impacting assay accuracy.
Area of Science:
- Biochemistry
- Clinical Chemistry
- Analytical Chemistry
Background:
- Apolipoprotein A-I (apoA-I) is a key component of high-density lipoprotein (HDL).
- Accurate measurement of apoA-I is crucial for cardiovascular risk assessment.
- Sample preparation and storage conditions can affect analyte stability.
Purpose of the Study:
- To compare the stability of apoA-I measurements in plasma versus heparin-manganese chloride (MnCl2) supernates.
- To investigate the impact of storage on apoA-I quantification in different sample matrices.
- To determine if MnCl2 affects apoA-I stability.
Main Methods:
- Radial immunodiffusion assay was used to measure apoA-I.
- Plasma and heparin-MnCl2 supernates were analyzed fresh and after seven days of storage at 4°C.
- Isolated HDL was treated with MnCl2 and stored to assess its effect on apoA-I.
Main Results:
- Fresh samples showed similar apoA-I values in plasma and heparin-MnCl2 supernates.
- After seven days of storage, apoA-I levels were significantly lower (>8%) in heparin-MnCl2 supernates compared to plasma.
- MnCl2 decreased apoA-I in isolated HDL, with a more pronounced effect after storage.
Conclusions:
- ApoA-I is less stable in heparin-MnCl2 supernates than in plasma, particularly after storage.
- The observed instability is likely due to an interaction between apoA-I and MnCl2.
- These findings highlight the importance of sample handling and storage for accurate apoA-I measurements.