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Physicochemical Characterization of Novikoff Hepatoma Mitochondrial DNA

Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92664

Mitochondrial DNA's (mtDNA) isolated from rat liver and the Novikoff hepatoma grown as both solid tumors and cells in monolayer culture were examined by a variety of physicochemical techniques. Buoyant densities in analytical CsCl equilibrium gradients and thermal denaturation profiles revealed no significant differences in base composition among the mtDNA's isolated from liver, tumor, and hepatoma cells. Sedimentation in neutral and alkaline CsCl showed no differences in mtDNA size. However, tumor and hepatoma cell mtDNA's were slightly smaller and more heterogeneous in size than liver mtDNA when molecular contour lengths were measured in the electron microscope. Based on chemical determinations, neoplastic mitochondria contained four to five times more DNA per mitochondrion than liver. Also, electron microscopy showed the proportion of mtDNA in complex forms (catenated dimers and oligomers) to be much higher in tumor (18%) and hepatoma cells (15%) than in liver (4%).

¹ Recipient of NIH Postdoctoral Fellowship 2FO CA51510-02 from the National Cancer Institute. Present address: Cancer Research Laboratory, University of California, Berkeley, Calif. 94720. To whom requests for reprints should be addressed.

² Recipient of NIH Grant CA11861.

³ Recipient of NSF Grant GB20674.

Received 7/31/74. Accepted 12/16/74.