ENZYME INHIBITION BY DERIVATIVES OF PHENOTHIAZINE

1952 ◽  
Vol 30 (6) ◽  
pp. 443-446
Author(s):  
H. B. Collier ◽  
G. M. Allenby
Keyword(s):  
Oxygen Uptake ◽  
Cytochrome Oxidase ◽  
Enzyme Inhibition ◽  
Rat Liver ◽  
Oxidase Activity ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Cytochrome Oxidase Activity ◽  
Derivatives Of

The succinoxidase activity of rat-liver mitochondria was strongly inhibited by the following compounds (concentration for 50% reduction in rate of oxygen uptake is given in brackets): phenothiazine (1.4 × 10−5 M), phenothiazine sulphoxide (2.8 × 10−5 M), and phenothiazone (5.4 × 10−5 M). Thionol was only slightly inhibitory. The cytochrome oxidase activity of mitochondria was not inhibited by any of these compounds.

Succinic and Cytochrome Oxidase Activity of Rat Liver Mitochondria After in Vitro Irradiation With Ultraviolet Light

1957 ◽  
Vol 188 (3) ◽  
pp. 547-549 ◽  
Author(s):  
Attilio Canzanelli ◽  
Rhea Sossen ◽  
David Rapport
Keyword(s):  
Cytochrome Oxidase ◽  
Ultraviolet Light ◽  
Rat Liver ◽  
Oxidase Activity ◽  
Biological Effects ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Cytochrome Oxidase Activity ◽  
Order Of Magnitude

Five per cent suspensions of rat liver mitochondria were irradiated with ultraviolet light for varying periods of time and the succinoxidase and cytochrome oxidase activity were determined. Both succinoxidase and cytochrome oxidase activity were reduced by irradiation with ultraviolet. The order of magnitude of the ultraviolet energy necessary to produce such changes is much less than that necessary to produce chemical changes in nucleic acid derivatives, and approaches the amount which has been shown to produce lethal and other biological effects.

scholarly journals The action of paraquat and diquat on the respiration of liver cell fractions

1968 ◽  
Vol 109 (5) ◽  
pp. 757-761 ◽  
Author(s):  
J C Gage
Keyword(s):  
Oxygen Uptake ◽  
Nadph Oxidase ◽  
Rat Liver ◽  
Oxidase Activity ◽  
Nadh Oxidase ◽  
Liver Microsomes ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Rat Liver Microsomes ◽  
Nadph Oxidase Activity

1. Paraquat and diquat produce only a slight increase in the oxygen uptake of rat liver mitochondria, and it is likely that they do not penetrate the mitochondrial membrane. 2. In mitochondrial fragments inhibited by antimycin A or by Amytal, both substances stimulate oxygen uptake with NADH or β-hydroxybutyrate as substrate but not with succinate. The NADH dehydrogenase of the respiratory chain appears to be involved, at a site only partially inhibited by Amytal. 3. An NADPH oxidase activity is stimulated in rat liver microsomes by diquat, and to a smaller extent by paraquat; diquat also causes an NADH oxidase activity to develop. The effect is not inhibited by carbon monoxide or p-chloromercuribenzoate, and it is probable that a flavoprotein is involved by a mechanism not requiring thiol groups. 4. One molecule of oxygen can oxidize two molecules of NADPH in the stimulated microsomal system, the hydrogen peroxide produced being broken down by a catalase activity in the microsomes. 5. Diquat can stimulate NADH oxidase and NADPH oxidase activity in the postmicrosomal soluble fraction; the enzyme involved may be DT-diaphorase. 6. The mechanism of these reactions and their significance in relation to the toxicity of the dipyridilium compounds are discussed.

scholarly journals Functional changes in rat liver mitochondria on administration of 2-methyl-4-dimethylaminoazobenzene

1984 ◽  
Vol 224 (3) ◽  
pp. 955-960 ◽  
Author(s):  
P Saikumar ◽  
C K R Kurup
Keyword(s):  
Electron Transfer ◽  
Cytochrome Oxidase ◽  
Rat Liver ◽  
Serum Cholesterol ◽  
Oxidase Activity ◽  
Mitochondrial Fraction ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Functional Changes ◽  
Succinate Oxidase

Administration of 2-methyl-4-dimethylaminobenzene in the diet (0.1%, w/w) for 85-90 days doubled the content of mitochondria in the livers of rats. The azodye was covalently bound to liver proteins, and about 15% of the amount found in liver was associated with the mitochondrial fraction. Mitochondria isolated from the livers of azodye-fed animals showed drastically lowered ability to oxidize NAD+-linked substrates. The inhibited electron-transfer step was the reduction of ubiquinone. The organelles showed a large increase in succinate oxidase activity. The activity of cytochrome oxidase and the content of cytochrome aa3 were substantially higher in these organelles. Azodye-fed animals showed depressed serum cholesterol concentrations. The content of ubiquinone in liver also registered a small increase.

Effect of 3,3′-di-iodothyronine and 3,5-di-iodothyronine on rat liver mitochondria

1993 ◽  
Vol 136 (1) ◽  
pp. 59-64 ◽  
Author(s):  
A. Lanni ◽  
M. Moreno ◽  
M. Cioffi ◽  
F. Goglia
Keyword(s):  
Cytochrome Oxidase ◽  
Rat Liver ◽  
Oxidase Activity ◽  
Mitochondrial Protein ◽  
The Other ◽  
Rat Liver Mitochondria ◽  
Mitochondrial Activity ◽  
Mitochondrial Mass ◽  
Cytochrome Oxidase Activity ◽  
Other Hand

ABSTRACT In the present study we report that 3,3′,5-tri-iodothyronine (T3) as well as two iodothyronines (3,5-diiodothyronine (3,5-T2) and 3,3′-di-iodothyronine (3,3′-T2)) significantly influence rat liver mitochondrial activity. Liver oxidative capacity (measured as cytochrome oxidase activity/g wet tissue) in hypothyroid compared with normal rats was significantly reduced (21%, P > 0·01) and the administration of T3 and both iodothyronines restored normal values. At the mitochondrial level, treatment with T3 stimulated respiratory activity (state 4 and state 3) and did not influence cytochrome oxidase activity. On the other hand, both the mitochondrial respiratory rate and specific cytochrome oxidase activity significantly increased in hypothyroid animals after treatment with 3,3′-T2 or 3,5-T2 (about 50 and 40% respectively). The actions of both iodothyronines were rapid and evident by 1 h after the injection. The hepatic mitochondrial protein content which decreased in hypothyroid rats (9·6 mg/g liver compared with 14·1 in normal controls, P < 0·05) was restored by T3 injection, while neither T2 was able to restore it. Our results suggest that T3 and both iodothyronines have different mechanisms of action. T3 acts on both mitochondrial mass and activity; the action on mitochondrial activity was not exerted at the cytochrome oxidase complex level. The action of the iodothyronines, on the other hand, is exerted directly on the cytochrome oxidase complex without any noticeable action on the mitochondrial mass. Journal of Endocrinology (1993) 136, 59–64

scholarly journals Proton translocation by the mitochondrial cytochrome b-c1 complex is inhibited by NN′-dicyclohexylcarbodi-imide

1982 ◽  
Vol 206 (2) ◽  
pp. 419-421 ◽  
Author(s):  
B D Price ◽  
M D Brand
Keyword(s):  
Electron Transport ◽  
Cytochrome Oxidase ◽  
Cytochrome B ◽  
Rat Liver ◽  
Proton Translocation ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Mitochondrial Cytochrome ◽  
Low Concentrations ◽  
Mitochondrial Cytochrome B

NN'-Dicyclohexylcarbodi-imide at low concentrations decreases the H+/2e ratio for rat liver mitochondria over the span succinate to oxygen from 5.9 +/- 0.3 (mean +/- S.E.M.) to 4.0 +/- 0.1 and for the cytochrome b-c1 complex from 3.8 +/- 0.2 to 1.9 +/- 0.1, but has little effect on the H+/2e ratio of cytochrome oxidase. The decrease in stoicheiometry is due, not to uncoupling or inhibition of electron transport, but to inhibition of proton translocation. NN'-Dicyclohexylcarbodi-imide thus ‘decouples’ proton translocation in the cytochrome b-c1 complex.

scholarly journals Evidence for the sequential assembly of cytochrome oxidase subunits in rat liver mitochondria

1983 ◽  
Vol 212 (3) ◽  
pp. 829-834 ◽  
Author(s):  
A Wielburski ◽  
B D Nelson
Keyword(s):  
Cytochrome Oxidase ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Temporal Sequence ◽  
Temporal Association ◽  
Rat Liver Mitochondria ◽  
Assembly Process ◽  
Isolated Rat Hepatocytes ◽  
Isolated Rat

The assembly of cytochrome oxidase was studied in isolated rat liver mitochondria and isolated rat hepatocytes labelled in vitro with L-[35S]methionine. This was achieved by studying the temporal association of radioactive subunits which are immunoabsorbed with antibodies against subunits I, II and the holoenzyme. Antibodies against the holoenzyme were shown to be highly specific for subunit V. The results show that subunit I appears in the holoenzyme late in the assembly process. No radioactive subunit I is absorbed with antiserum against subunit II or the holoenzyme (subunit V) after a 30 min pulse in either isolated mitochondria or hepatocytes. However, both antisera absorb radioactive subunits I after a 150 min chase in isolated hepatocytes. This was confirmed using antibodies against subunit I, which absorbed only radioactive subunit I after a 30 min pulse but absorbed radioactive subunits I-III and VI after a 150 min chase. Thus, the late assembly of radioactive subunit I is explained by a temporal sequence in the assembly process and not by the presence of a large, non-radioactive pool of subunit I. Using the above approach and the three specific antisera, the following temporal sequence in the assembly of cytochrome oxidase was established. Subunits II and III assemble rapidly with each other or with cytoplasmically translated subunit VI. This complex of three peptides in turn assembles slowly with subunit I or with the other cytoplasmically translated subunits. The early association of subunit VI with the mitochondrially translated subunits II and III suggests a possible role of the former in integration of the holoenzyme.

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