Differences in Total Mitochondrial Proteins and Proteins Synthesized by Mitochondria from Rat Liver and Morris Hepatomas 9618A, 5123C, and 5123tc1

Mitochondria were isolated from a slow-growing (9618A) and two intermediate-to-fast-growing (5123C, 5123tc) Mor ris hepatomas and host livers. The mitochondria! proteins were solubilized and fractionated on sodium dodecyl sulfate:polyacrylamide slab gels. One Coomassie bluestained band was absent or reduced in amount in all tumors relative to host livers. In addition, a major mito chondria! enzyme present in normal liver, carbamyl phos phate synthetase, was missing or greatly reduced in the slow-growing, highly differentiated hepatoma 9618A, a tumor that is considered to be similar to normal liver in many biochemical and morphological respects. Incuba tion of mitochondria with [35S]methionine and a suitable amino acid incorporation system resulted in labeling of specific mitochondria! proteins. Autoradiography of the slab gels disclosed four prominently labeled fractions and a number of minor fractions. Preparations from hepatoma 5123tc demonstrated two labeled bands that were absent or greatly reduced in host liver. Host liver preparations displayed a minor band that was absent or greatly re duced in hepatoma 5123C. However, no single change in labeling pattern was common to all three tumors, sug gesting the absence of a causal relationship between carcinogenesis and mutations in mitochondria! DMA.