Structural and functional changes in Novikoff hepatoma mitochondria.

Novikoff hepatoma mitochondria were studied with regard to their functional and structural organization. The activities of cytochrome oxidase and malate dehydrogenase in mitochondria purified on sucrose gradients were similar in organdÃ-es derived from normal liver and hepatoma tissue. However, the activities of reduced nicotinamide adenine dinucleotide oxidase and succinate oxidase in hepatoma mitochondria were reduced to only 10 and 35%, respectively, of the activities in liver mitochondria. Also, monoamine oxidase and rotenone-insensitive reduced nico tinamide adenine dinucleotide-cytochrome c reducÃ-ase(en zymes localized in the outer mitochondria! membrane) have significantly reduced activities in hepatoma mitochondria. The structural changes in hepatoma mitochondria might be correlated with differences in the banding patterns of liver and hepatoma mitochondria in sucrose gradients. While liver mitochondria banded sharply at a density of 1.187 g/ml, as evidenced by marker enzyme activity and protein assay, hepatoma mitochondria were heterogeneous, band ing over a density range of 1.144 to 1.161 g/ml. The addition of 1% bovine serum albumin to the isolation medium increased the density of hepatoma mitochondria in sucrose gradients to 1.171 g/ml and resulted in sharp, homogeneous bands. This increase in density is due in part to protein binding, as evidenced by bovine serum albumin"C-binding experiments. In addition, hepatoma mito