An ultrastructural study of opaque cytoplasmic inclusions induced by triparanol treatment

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Abstract
The administration of triparanol caused an hypertrophy of smooth membranes and the occurrence of numerous cytoplasmic bodies in smooth muscle fibers and parasympathetic ganglion cells in the myenteric plexus of the hamster ileum. The hypertrophied membranes were more evident in the early stages of treatment when the cytoplasmic bodies were relatively few in number. The cytoplasmic bodies were tentatively divided into four types as follows: whorls of membranes (type I), labyrinthine aggregates of smooth membranes (type II), dense bodies with a reticular internal structure (type III) and crystalline bodies showing a regular lattice pattern (type IV). There were also many intermediate types of cytoplasmic bodies which exhibited more than one characteristic of the types mentioned above. The relative numbers of the cytoplasmic bodies seemed to be increased in the order of type I (or type II), type III, and type IV in proportion to the period of treatment. It is suggested that type IV cytoplasmic bodies are formed through the stages of type I (or type II) and type III, and that types I, II, and III in turn, form from hypertrophied smooth membranes. The formation of crystalline bodies from hypertrophied membranes may represent the inclusion of cytoplasmic organelles into autophagic vacuoles (lysis). After certain degrees of lysis, more resistant components of the hypertrophied membranes remain as residues. These residues, rich in phospholipids, are probably represented as crystalline bodies.