[Interaction of serum albumin with apoprotein E and very low density lipoproteins in human blood].

The complex formation between apolipoprotein E (apoE) isolated from human plasma very low density lipoproteins (VLDL) and human serum albumin (HSA) in both native and fully reduced states has been studied. Using measurements of fluorescence anisotropy and fluorescence intensity of the fluorescein-labelled apoE, the elution profiles of the apoE/HSA complex and the kinetics of the protein cross-linking within the complex by a water-soluble bifunctional reagent, the existence of a kinetically unstable complex of apoE with native albumin has been shown. The complex became more stable after the reduction of the S-S links in the albumin molecules capable of forming aggregates under these conditions. The interaction between native HSA as opposed to the fully reduced one and the isolated VLDL particles was far more pronounced, apparently due to the existence of amphipathic alpha-helical regions. It is suggested that the ability of the apolipoprotein to interact with albumin is determined by the inner stability of the albumin molecular structure and that the complexes detected in vitro may be regarded as a new transport form of apolipoproteins in a lipid-free form in the serum.