Fine Structure of Transplantable Hepatomas of the Rat2

The fine structure of 6 hepatomas representing wide variability in rates of growth has been investigated. These include 2 fast-growing tumors, Novikoff and Morris 3683, 2 ethionine-induced tumors with intermediate growth rates, and 2 slow-growing tumors, Reuber H-35 and Morris 5123. The fine structure of each hepatoma is characteristic. Common to all hepatomas are large nucleoli, a large Golgi complex, and the presence of numerous free ribosomes arranged in clusters. The fast-growing hepatomas have a simple organization of the cytoplasm. The slow-growing hepatomas have better developed and more organized cytoplasmic membrane systems, including well-developed rough and smooth endoplasmic reticulum. Stacks of rough cisternae are-best developed in the slow-growing Reuber H-35 hepatoma. Mitochondria are smaller and have fewer cristae in the rapidly growing hepatomas and are larger and more hepatocyte-like in the slow-growing tumors. Nevertheless, the structure of slow-growing hepatomas never resembles that of normal hepatocytes in complexity. It is suggested that major differences between hepatomas can be attributed to three factors: growth rate of the tissue, its genetic and developmental history, and, indirectly, to nutritional factors and tumorhost relationship.