scholarly journals Sites of inhibition of mitochondrial electron transport in macrophage-injured neoplastic cells.

1982 ◽  
Vol 95 (2) ◽  
pp. 527-535 ◽  
Author(s):  
D L Granger ◽  
A L Lehninger
Keyword(s):  
Electron Transport ◽  
Respiratory Chain ◽  
Mitochondrial Respiration ◽  
Intact Cell ◽  
Coenzyme Q ◽  
Mitochondrial Respiratory Chain ◽  
Neoplastic Cells ◽  
L1210 Cells ◽  
Time Courses ◽  
A Minor

Previous work has shown that injury of neoplastic cells by cytotoxic macrophages (CM) in cell culture is accompanied by inhibition of mitochondrial respiration. We have investigated the nature of this inhibition by studying mitochondrial respiration in CM-injured leukemia L1210 cells permeabilized with digitonin. CM-induced injury affects the mitochondrial respiratory chain proper. Complex I (NADH-coenzyme Q reductase) and complex II (succinate-coenzyme Q reductase) are markedly inhibited. In addition a minor inhibition of cytochrome oxidase was found. Electron transport from alpha-glycerophosphate through the respiratory chain to oxygen is unaffected and permeabilized CM-injured L1210 cells oxidizing this substrate exhibit acceptor control. However, glycerophosphate shuttle activity was found not to occur within CM-injured or uninjured L1210 cells in culture hence, alpha-glycerophosphate is apparently unavailable for mitochondrial oxidation in the intact cell. It is concluded that the failure of respiration of intact neoplastic cells injured by CM is caused by the nearly complete inhibition of complexes I and II of the mitochondrial electron transport chain. The time courses of CM-induced electron transport inhibition and arrest of L1210 cell division are examined and the possible relationship between these phenomena is discussed.

Regulation of mitochondrial respiration in eggs and embryos of sea urchin

Zygote ◽  
1999 ◽  
Vol 8 (S1) ◽  
pp. S3-S4
Author(s):  
Ikuo Yasumasu
Keyword(s):  
Electron Transport ◽  
Respiratory Rate ◽  
Respiratory Chain ◽  
Sea Urchin ◽  
Mitochondrial Respiration ◽  
Atp Release ◽  
Mitochondrial Respiratory Chain ◽  
High Concentration ◽  
Respiratory Systems ◽  
Mitochondrial Respiratory

It is well known that sea urchin eggs, which exhibit quite a low rate of respiration before fertilisation, undergo a sudden increase in the rate of respiration followed by its gradual decrease in about a 15 min period after fertilisation (Ohnishi & Sugiyama, 1963; Epel, 1969), in which the respiration is mediated mainly by Ca2+-activated non-mitochondrial respiratory systems (Foerder et al., 1978; Perry & Epel, 1985a,b). During this short period the rate of mitochondrial respiration gradually increases (Yasumasu et al., 1988) and stabilises at a higher rate than before fertilisation (Warburg, 1908, 1910; Whitaker, 1933; Yasumasu & Nakano, 1963), when the respiration due to non-mitochondrial respiratory systems is turned off. The rate of mitochondrial respiration, once enhanced upon fertilisation, increases further in the period between hatching and the gastrula stage, without any changes in the number of mitochondria or the capacity of electron transport in the mitochondrial respiratory chain (Fujiwara & Yasumasu, 1997; Fujiwara et al., 2000). It is likely that the respiratory rate is reduced by regulation of electron transport in the mitochondrial respiratory chain and increases due to the release of electron transport from the regulation upon fertilisation and after hatching.A marked increase in the respiratory rate after hatching is accompanied by an evident decrease in the ATP level without any change in the levels of ADP and AMP (Mita & Yasumasu, 1984). In isolated mitochondria, the rate of respiration, estimated in the presence of ADP at the same concentration as in embryos, is reduced by a high concentration of ATP as found in embryos before hatching but is not affected at a concentration as low as in gastrulae (Fujiwara & Yasumasu, 1997; Fujiwara et al., 2000) ATP at a high concentration probably blocks ATP release from mitochondria and consequently inhibits ADP uptake coupled to ATP release in the ATP/ADP translocation reaction in the mitochondrial membrane, causing a shortage of intra-mitochondrial ADP.

Coenzyme Q: potentially useful index of bioenergetic and oxidative status of spermatozoa

1995 ◽  
Vol 41 (2) ◽  
pp. 217-219 ◽  
Author(s):  
A G Angelitti ◽  
L Colacicco ◽  
C Callà ◽  
M Arizzi ◽  
S Lippa
Keyword(s):  
Respiratory Chain ◽  
Coenzyme Q10 ◽  
Coenzyme Q ◽  
Mitochondrial Respiratory Chain ◽  
Oxidative Status ◽  
Atp Production ◽  
The Difference ◽  
Autoregulatory Mechanism ◽  
Infertile Patients ◽  
Mitochondrial Respiratory

Abstract The concentration of coenzyme Q10 (CoQ10), a key intermediate of the mitochondrial respiratory chain, was determined in spermatozoa of 13 fertile subjects, 8 potentially fertile patients, and 12 infertile patients. CoQ10 concentrations were significantly higher (P < 0.001) in infertile patients than in fertile and potentially fertile subjects. The difference between potentially fertile and fertile subjects was also significant (P < 0.001). We propose that a decrease in consumption of CoQ10 in both infertile and potentially fertile populations is due to an autoregulatory mechanism of ATP production.

scholarly journals Kinetics of integrated electron transfer in the mitochondrial respiratory chain: random collisions vs. solid state electron channeling

2007 ◽  
Vol 292 (4) ◽  
pp. C1221-C1239 ◽  
Author(s):  
Giorgio Lenaz ◽  
Maria Luisa Genova
Keyword(s):  
Respiratory Chain ◽  
Coenzyme Q ◽  
Lateral Diffusion ◽  
Kinetic Studies ◽  
Mitochondrial Respiratory Chain ◽  
Substrate Channeling ◽  
Solid State Electron ◽  
Native Electrophoresis ◽  
Redox Molecules ◽  
Mitochondrial Respiratory

Recent evidence, mainly based on native electrophoresis, has suggested that the mitochondrial respiratory chain is organized in the form of supercomplexes, due to the aggregation of the main respiratory chain enzymatic complexes. This evidence strongly contrasts the previously accepted model, the Random Diffusion Model, largely based on kinetic studies, stating that the complexes are randomly distributed in the lipid bilayer of the inner membrane and functionally connected by lateral diffusion of small redox molecules, i.e., coenzyme Q and cytochrome c. This review critically examines the experimental evidence, both structural and functional, pertaining to the two models and attempts to provide an updated view of the organization of the respiratory chain and of its kinetic consequences. The conclusion that structural respiratory assemblies exist is overwhelming, whereas the expected functional consequence of substrate channeling between the assembled enzymes is controversial. Examination of the available evidence suggests that, although the supercomplexes are structurally stable, their kinetic competence in substrate channeling is more labile and may depend on the system under investigation and the assay conditions.

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