Fine Structure of Hepatomas Induced in Rats With p-Dimethylaminoazobenzene23

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Abstract
The cells of malignant hepatomas induced by p-dimethylaminoazobenzene (DAB) showed many ultrastructural differences from normal liver cells, from the cells of Morris or Reuber hepatomas, and from hepatomas induced with ethionine. The deviations involved both cytoplasm and nucleus. Mitochondria, in addition to decrease in number and marked deformity of their profiles, showed large, dense, matrix granules with loss of and tubular transformation of cristae and vacuolization of matrix. The dense granules may represent an abnormality of ionic sequestration or substrate trapping as a result of deletion of mitochondrial enzymes. The wide variations in endoplasmic reticulum (ER), both in quantity and patterns assumed, indicated little correlation between ER structure and degree of malignancy. The disordered protein synthesis by these tumor cells may be related to the marked dispersion of ribosomes throughout their cytoplasm. Annulate lamellae were prominent. Cytoplasmic bodies, containing altered organelles and rich in acid phosphatase, were common in DAB-induced hepatomas. Loose and compact aggregates of fibrils, probably representing early subcellular metaplasia, were prominent in cytoplasm of many tumor cells. In nuclei, the pars amorpha was commonly present and increased in size. Interchromatinic granules and nuclear pores were present. Adenocarcinomas were composed of cells that resembled biliary epithelial cells in their ultrastructure. Moreover, the acini were bound by a basement membrane. These two observations are interpreted to indicate origin of adenocarcinomas, as well as cystic structures, from bile ducts. There were no uniform ultrastructural differences between primary and metastatic tumors.