Plasma lipoproteins in rats with experimental biliary obstruction. II. An ultrastructural study.

Acute biliary obstruction in the rat is associated with abnormalities of the ultrastructure of plasma lipoproteins. 1.1. The d < 1.006 g/ml fraction contains two types of particles: (a) vesicles having a mean diameter of 42.0 nm and (b) spheroidal particles which have a mean diameter of 80.0 nm. The latter show surface irregularities which make these particles appear as spherical bodies with holes.2.2. The d 1.019–1.063 g/ml fraction is heterogeneous. Gel filtration on 2% agarose allows the characterization of three components designated subfraction I, II and III respectively. Subfraction I is composed of large aggregates of spherical and vesicular particles. Subfraction II consists of 50.0–80.0 nm vesicles which show strong similarities to artificially prepared emulsions of phospholipids in water. Subfraction III contains particles which have a mean diameter of 20.0 nm and resemble low density lipoproteins of normal rats.3.3. The d 1.063–1.125 g/ml fraction contains 35.0 nm discoidal particles which tend to form ruleaux with a periodicity of 4.9 nm. This fraction also contains a few vesicles and 10.0 nm spherical particles similar to those found in the corresponding fraction of normal rat.