Mitochondrial ATPase activities of hepatoma BW7756 and ascites tumor cells. Influence of MG2+ ions, free fatty acids, and uncouplers.

1.

Intact Ehrlich ascites tumour cells exhibit a residual respiration which is insensitive to site-specific inhibitors of mitochondrial electron transport. Treatment of the tumour-bearing mice with phenobarbital does not influence the rate of this inhibitor-resistant respiration.




2.

Among the respiratory pigments analysed spectrophotometrically in the microsomal fraction prepared from ascites cells, only small amounts of flavoproteins (NADH-cytochrome b5 reductase and NADPH-cytochrome c reductase) were detectable.




3.

Ascites-cell nuclei respire with NADH or NADPH, but not with succinate, as substrates and the respiration is unaffected by inhibitors of mitochondrial electron and energy transfer. These nuclei contain cytochrome b5, whereas cytochrome P-450 or mitochondrial-like cytochromes are lacking.




4.

It is concluded that the NAD(P)H-dependent electron transport in nuclei is responsible for the inhibitor-insensitive O2 uptake of intact cells. Conversely, mixed function oxidation reactions of the endoplasmic reticulum have no role in this connection. Moreover, it is assumed that nuclear respiration is involved in the control of the cellular redox potential.




5.

The relevance of the data obtained with respect to some assumptions concerning the biogenesis of the endoplasmic reticulum is discussed.

Respiratory activity of Ehrlich ascites tumour cell nuclei.

An abnormal ratio of cytochromes in the respiratory chain of mouse and human myelomas.

— Dual wavelength reflection spectrophotometry was used to determine steady state changes in the reduction-oxidation ratio of cytochrome c oxidase (a,a3) and vascular reactivity accompanying progressive growth of cortical and subcutaneous astrocytomas and neuroblastomas in vivo. Blood volume responses indicate that vessels invading the tumors retain regulatory reactivity typical of the body region of implantation and do not acquire those typical of the tissue of origin of the neoplastic cells. In comparison with non neoplastic tissue, early stage tumor growth was associated with highly oxidized ratios of cytochrome a,a3. A transition to highly reduced cytochrome a,a3 occurred during late stage tumor development. Such differences from normal cerebral tissues reflect alterations in micro-circulation and respiratory chain function accompanying the dynamics of tumor growth, and could provide a basis for selective therapeutic measures.

Redox properties of cytochrome oxidase and vascular reactivity of astrocytomas and neuroblastomas in vivo.

To investigate the possibility that mitochondrial transcription could be altered in tumours we started by characterizing the RNA obtained from mitochondria, isolated from Walker carcinosarcoma and purified by a procedure devised to compensate for the lower size and density of these organelles in 10-day tumours. The RNA was extracted by the 'hot phenol' technique and analysed by electrophoresis in 2.7 and 2.5% polyacrylamide gels at different running times, identifying the usual cytoplasmic contaminants 28 and 18S peaks plus the other five major peaks at 40, 20.5, 16.3, 15.4, and 4Se. The 28 and 18Se peaks were not eliminated by digitonin treatment of the mitochondria, indicating that they arise from cytoplasmic ribosomes tightly associated with the mitochondria. From its sensitivity to DNAase (deoxyribonuclease), resistance to RNAase (ribonuclease) and coincidence with external marker DNA, the 40Se peak was identified as containing mainly DNA. Sucrosegradient centrifugation for different periods showed a major component at 16.2S, the 28 and 18S cytoplasmic RNA species, peaks at 13.8, 6.4 and 4S and a small 19.5S peak. By polyacrylamide-gel electrophoresis of the purified RNA classes separated by one or two cycles of centrifugation, the following correlation were established: 20.5Se19.5S; 16.3Se16.2S; 15.4Se13.8S. The 6.4S RNA ran as a mixture of 4 and 4.7Se species. When the 20.5Se and 15.4Se RNA species were centrifuged, they behaved as 16.2S and 13.8S respectively, thus suggesting that the 16.2S (16.3Se) arises by cleavage from the 19.5S(20.5Se), the 13.8S (15.4Se) being the other RNA from mitochondrial ribosomes.

Electrophoretic and centrifugation behaviour of mitochondrial ribonucleic acid from Walker 256 carcinosarcoma.

Pathways of intracellular hydrogen transport in the Walker carcinosarcoma 256. I. The intramitochondrial electron transport and the translocation of reducing equivalents across the mitochondrial membrane.

O. Dionisi

Papers

Pathways of intracellular hydrogen transport in the Walker carcinosarcoma 256. I. The intramitochondrial electron transport and the translocation of reducing equivalents across the mitochondrial membrane.