scholarly journals Fine Structural Alterations in Cell Particles During Chemical Carcinogenesis

1960 ◽  
Vol 7 (1) ◽  
pp. 49-60 ◽  
Author(s):  
Joseph C. Arcos ◽  
George W. Griffith ◽  
Richard W. Cunningham
Keyword(s):  
Ph Dependence ◽  
Chemical Carcinogenesis ◽  
Normal Liver ◽  
Liver Mitochondria ◽  
Unit Weight ◽  
Rat Liver Mitochondria ◽  
Swelling Properties ◽  
Carcinogenic Process ◽  
Sulfhydryl Compounds

Swelling under carefully controlled conditions has been used to study alterations in the structure of rat liver mitochondria as a result of feeding azo dyes. The changes of the swelling properties of the mitochondria during feeding of the hepatocarcinogenic 3'-methyl-4-dimethylaminoazobenzene are essentially comparable to those observed previously with the microsomes, under the same dietary conditions. These alterations in mitochondrial swelling are not related to changes in the amount of these cell particulates per unit weight of tissue, during feeding of this azo dye. As with the microsomes, feeding of the isomeric but relatively noncarcinogenic 2-methyl-4-dimethylaminoazobenzene does not affect swelling. The structural differences between liver and hepatoma mitochondria show up not only in the rate and extent of swelling but also in the form of the curves of pH dependence. The influence of ketones and sulfhydryl compounds on the swelling of normal liver mitochondria were studied, with particular emphasis to the role of sulfhydryl groups in membrane permeability. The sudden steep rise in the tumor incidence in groups of rats fed 3'-methyl-4-dimethylaminoazobenzene for increasing intervals of time occurs at about 4 weeks. This time correlates with the point of the minimum swelling of microsomes and mitochondria isolated from the livers of rats fed this same dye. Thus, a correlation is established between the alterations of the swelling properties of these particulates and the carcinogenic process.

Role of calcium and superoxide dismutase in sensitizing mitochondria to peroxynitrite-induced permeability transition

2004 ◽  
Vol 286 (1) ◽  
pp. H39-H46 ◽  
Author(s):  
Paul S. Brookes ◽  
Victor M. Darley-Usmar
Keyword(s):  
Superoxide Dismutase ◽  
Cytochrome C ◽  
Rat Liver ◽  
Permeability Transition ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Isolated Rat Liver ◽  
Ptp Opening ◽  
Isolated Rat

The mitochondrial permeability transition pore (PTP) is a membrane protein complex assembled and opened in response to Ca2+ and oxidants such as peroxynitrite (ONOO–). Opening the PTP is mechanistically linked to the release of cytochrome c, which participates in downstream apoptotic signaling. However, the molecular basis of the synergistic interactions between oxidants and Ca2+ in promoting the PTP are poorly understood and are addressed in the present study. In isolated rat liver mitochondria, it was found that the timing of the exposure of the isolated rat liver mitochondria to Ca2+ was a critical factor in determining the impact of ONOO– on PTP. Specifically, addition of Ca2+ alone, or ONOO– and then Ca2+, elicited similar low levels of PTP opening, whereas ONOO– alone was ineffective. In contrast, addition of Ca2+ and then ONOO– induced extensive PTP opening and cytochrome c release. Interestingly, Cu/Zn-superoxide dismutase enhanced pore opening through a mechanism independent of its catalytic activity. These data are consistent with a model in which Ca2+ reveals a molecular target that is now reactive with ONOO–. As a test of this hypothesis, tyrosine nitration was determined in mitochondria exposed to ONOO– alone or to Ca2+ and then ONOO–, and mitochondrial membrane proteins were analyzed using proteomics. These studies suggest protein targets revealed by Ca2+ include dehydrogenases and CoA-containing enzymes. These data are discussed in the context of the role of mitochondria, Ca2+, and ONOO– in apoptotic signaling.

scholarly journals Characterization of the effects of Ca2+ on the intramitochondrial Ca2+-sensitive enzymes from rat liver and within intact rat liver mitochondria

1985 ◽  
Vol 231 (3) ◽  
pp. 581-595 ◽  
Author(s):  
J G McCormack
Keyword(s):  
Rat Liver ◽  
Pyruvate Dehydrogenase ◽  
Liver Mitochondria ◽  
Ruthenium Red ◽  
Pyruvate Dehydrogenase Kinase ◽  
Rat Liver Mitochondria ◽  
Mitochondrial Inner Membrane ◽  
Mammalian Tissues ◽  
14Co2 Production

The regulatory properties of the Ca2+-sensitive intramitochondrial enzymes (pyruvate dehydrogenase phosphate phosphatase, NAD+-isocitrate dehydrogenase and 2-oxoglutarate dehydrogenase) in extracts of rat liver mitochondria appeared to be essentially similar to those described previously for other mammalian tissues. In particular, the enzymes were activated severalfold by Ca2+, with half-maximal effects at about 1 microM-Ca2+ (K0.5 value). In intact rat liver mitochondria incubated in a KCl-based medium containing 2-oxoglutarate and malate, the amount of active, non-phosphorylated, pyruvate dehydrogenase could be increased severalfold by increasing extramitochondrial [Ca2+], provided that some degree of inhibition of pyruvate dehydrogenase kinase (e.g. by pyruvate) was achieved. The rates of 14CO2 production from 2-oxo-[1-14C]glutarate at non-saturating, but not at saturating, concentrations of 2-oxoglutarate by the liver mitochondria (incubated without ADP) were similarly enhanced by increasing extramitochondrial [Ca2+]. The rates and extents of NAD(P)H formation in the liver mitochondria induced by non-saturating concentrations of 2-oxoglutarate, glutamate, threo-DS-isocitrate or citrate were also increased in a similar manner by Ca2+ under several different incubation conditions, including an apparent ‘State 3.5’ respiration condition. Ca2+ had no effect on NAD(P)H formation induced by β-hydroxybutyrate or malate. In intact, fully coupled, rat liver mitochondria incubated with 10 mM-NaCl and 1 mM-MgCl2, the apparent K0.5 values for extramitochondrial Ca2+ were about 0.5 microM, and the effective concentrations were within the expected physiological range, 0.05-5 microM. In the absence of Na+, Mg2+ or both, the K0.5 values were about 400, 200 and 100 nM respectively. These effects of increasing extramitochondrial [Ca2+] were all inhibited by Ruthenium Red. When extramitochondrial [Ca2+] was increased above the effective ranges for the enzymes, a time-dependent deterioration of mitochondrial function and ATP content was observed. The implications of these results on the role of the Ca2+-transport system of the liver mitochondrial inner membrane are discussed.

scholarly journals Studies on the activation of rat liver pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase by adrenaline and glucagon. Role of increases in intramitochondrial Ca2+ concentration

1985 ◽  
Vol 231 (3) ◽  
pp. 597-608 ◽  
Author(s):  
J G McCormack
Keyword(s):  
Rat Liver ◽  
Pyruvate Dehydrogenase ◽  
Liver Mitochondria ◽  
Active Enzyme ◽  
Female Rats ◽  
Rat Liver Mitochondria ◽  
Na Ions ◽  
Oxoglutarate Dehydrogenase

The administration in vivo of either adrenaline or glucagon alone resulted in increases of about 2-fold in the amounts of active, non-phosphorylated, pyruvate dehydrogenase in the livers of fed male or female rats, whereas when administered together increases of about 4-fold were obtained. Ca2+-dependent increases in the amount of active enzyme of up to about 5-fold could be achieved in isolated rat liver mitochondria by incubating them with increasing extramitochondrial [Ca2+]; from this, two conditions of Ca loading were chosen which caused increases in active enzyme similar to those with the hormone treatments given above. The increases in enzyme activity owing to these Ca loads persisted through the ‘re-isolation’ of mitochondria and their incubation in Na+-free KCl-based media containing EGTA. Differences from values obtained with unloaded controls could be diminished by adding Na+ ions to cause the egress of Ca2+ from the mitochondria, or enough extramitochondrial Ca2+ to saturate the enzyme in its Ca2+-dependent activation; the effects of Na+ could be blocked by diltiazem, an inhibitor of mitochondrial Na+/Ca2+ exchange. The re-isolated, Ca-preloaded, mitochondria also exhibited enhanced activities of 2-oxoglutarate dehydrogenase when assayed at non-saturating [2-oxoglutarate] by two different methods; effects of Na+, Ca2+ or diltiazem on the persistent activations of this enzyme were similar to those for pyruvate dehydrogenase. Na+ caused a marked depletion, which could be blocked by diltiazem, of the 45Ca content of re-isolated mitochondria which had pre-loaded with Ca, containing 45Ca, to the same degrees as above. The activities of pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase in incubated liver mitochondria prepared from rats subjected to the hormone treatments given above were found to behave in a very similar manner to those exhibited in the re-isolated, Ca-preloaded, mitochondria. It is concluded that these hormones each bring about the activations of these rat liver enzymes by causing increases in intramitochondrial [Ca2+], and that their effects, as such, are additive.

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