A comparison of some ultrastructural and biochemical properties of mitochondria from Morris hepatomas 9618A, 7800, and 3924A.

condensed densely staining matrices surrounded by intact inner and outer membranes, and acceptor control ratios near 5 with 0-hydroxybutyrate as substrate. Mitochondria from the rapidly growing hepatoma 3924A, in contrast to those from hepatomas 96ISA and 7800 and from host liver, have diluted-appearing matrices, fail to oxidize 0-hydroxybutyrate, and have low acceptor control ratios in the presence of succinate as substrate. Addition of 2,4-dinitrophenol enhances the respiratory activity of mitochondria from all three hepatomas. Assays for cytochrome oxidase, malate dehydrogenase, adenylate kinase, and monoamine oxidase, showed that only the specific activity of the latter enzyme is low in mito chondria from all hepatomas studied. The specific activity of adenylate kinase is low in mitochondria from hepatomas 7800 and 3924A, but near normal in mitochondria from hepatoma 96ISA. The specific activities of cytochrome oxidase and malate dehydrogenase are about as high in hepatoma mitochondria as in mitochondria from host livers. With respect to those properties examined, these studies clearly show that mitochondria from the most rapidly growing heptoma, 3924A, bear the least resemblance to host liver mitochondria, whereas mitochondria from hepatomas 9618A and 7800 are very similar to but not identical with control mitochondria.