Loss of human serum apolipoproteins C and E during manipulation of diluted solutions

The adsorption of human serum very low density apolipoproteins C-I, C-II, C-III, and E to the interior surfaces or Beckman Airfuge plastic tubes and glass pipettes has been studied. 125I-Labeled apolipoprotein C-III-1 (1 microgram/ml) was used as a model compound to study the adsorption. After 60 min about 45% was bound to the tube walls, and 5-10% bound rapidly to the pipette used for removing the solution from the tube. Addition of increasing amounts of non-labeled apolipoprotein C-I, C-II, C-III, or E to the tubes reduced the amount of labeled C-III on the tube walls, indicating a strong affinity of these apolipoproteins for the surface. The results demonstrate the importance of careful control of the different steps in immunological ultramicroquantitation methods, that might be influenced by adsorption-losses of the apolipoproteins.