Use of constant composition polyvinylpyrrolidone columns to study the interaction of fat particles with plasma.

Fat particles (lipoproteins of S(f) > 400) have been obtained from dog and human lymph and from human post-alimentary plasma. They were flocculated by a solution of 5% polyvinylpyrrolidone (PVP) in 10% NaCl and layered at the bottom of tubes of PVP of various concentrations between 2% and 5% (w/v). As the concentration of PVP increased, a greater proportion of the particles accumulated at the top of the tube ("primary" particles). When the concentration of PVP in the tube was held constant at 3% PVP, dilution of the sample with plasma was found to produce an increased proportion of bottom particles ("secondary" particles). This observation suggests that bottom particles result from an interaction of top particles with plasma.