Macromolecular assemblies of lipid in bile

1. 1. Calculous and acalculous natural bile, and aqueous dispersions of cholesterol, conjugated bile salts and phospholipid which resemble both kinds of natural bile, have been investigated by the negative-staining technique of electron microscopy, with the aim of obtaining data on the shape and size of mixed micelles of lipid and bile salts occurring in normal and pathological bile. 2. 2. Two main kinds of macromolecular assembly were seen. One of these, which was present in both calculous and acalculous bile, apparently owes its characteristic appearance to the presence of bile salts, since similar structures were observed in “artificial” bile. This assembly was interpreted in terms of a specific arrangement of disc-shaped, mixed micelles of lipid and bile salt molecules. The structure of the other assembly observed closely resembles that of “liposomes” which occur in dispersions of phospholipid and cholesterol free from bile salts. 3. 3. No significant differences were found between the negatively stained preparations of calculous and acalculous bile. It is suggested, however, that the growth of cholesterol-containing gall stones in pathological bile which is relatively deficient in bile salts may be associated with the presence of liposomes.