scholarly journals Ketogenesis in isolated rat liver mitochondria I. Relationships with the citric acid cycle and with the mitochondrial energy state

1972 ◽  
Vol 283 (1) ◽  
pp. 1-15 ◽  
Author(s):  
M. Lopes-Cardozo ◽  
S.G. Van Den Bergh
Keyword(s):  
Citric Acid ◽  
Rat Liver ◽  
Citric Acid Cycle ◽  
Energy State ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Acid Cycle ◽  
Isolated Rat Liver ◽  
Isolated Rat

scholarly journals Studies on the efflux of metalloporphyrin from isolated rat liver mitochondria. Effect of respiratory substrates and metabolic inhibitors

1982 ◽  
Vol 202 (1) ◽  
pp. 41-46 ◽  
Author(s):  
P Husby ◽  
I Romslo
Keyword(s):  
Membrane Potential ◽  
Rat Liver ◽  
Incubation Medium ◽  
Energy State ◽  
Liver Mitochondria ◽  
Metabolic Inhibitors ◽  
Rat Liver Mitochondria ◽  
Isolated Rat Liver ◽  
Isolated Rat

Intramitochondrially synthesized Co-deuteroporphyrin is released to the incubation medium at a rate inversely correlated to the energy state of the mitochondria; i.e. the rate of efflux increases when substrate is depleted, respiration inhibited or the mitochondria are uncoupled. The efflux of Co-deuteroporphyrin from mitochondria remains low as long as the residual membrane potential is above one-third that of maximally energized mitochondria. Globin enhances the efflux of Co-deuteroporphyrin not only from mitochondria depleted of substrates [Husby & Romslo (1980) Biochem. J. 188, 459-465], but also from maximally energized mitochondria. The results provide further evidence for a co-operative mechanism between the mitochondria and their surroundings for the mobilization of metalloporphyrin from mitochondria.

scholarly journals Studies on the efflux of metalloporphyrin from rat liver mitochondria. Effect of K+ and other cations

1981 ◽  
Vol 196 (2) ◽  
pp. 451-457 ◽  
Author(s):  
P Husby ◽  
I Romslo
Keyword(s):  
Ionic Strength ◽  
Rat Liver ◽  
Incubation Medium ◽  
Energy State ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Isolated Rat Liver ◽  
Sucrose Medium ◽  
Low Ionic Strength ◽  
Isolated Rat

The mechanism by which metalloporphyrins synthesized within the mitochondria escape to the incubation medium was studied in isolated rat liver mitochondria. In a low-ionic-strength sucrose medium, the efflux of metalloporphyrins is markedly decreased when K+ (greater than 10 mM) is added. The effect of K+ is not dependent on the energy state of the mitochondria and it can in part be abolished by adding globin, but not albumin. K+ also decreases the uptake of porphyrins by the mitochondria and thereby the rate of synthesis of metalloporphyrins. Qualitatively similar results are found with Na+, Li+, Mg2+ and Ca2+. Quantitatively, however, the efficiency of cations to inhibit the release of metalloporphyrins decreases in the order: Mg2+ greater than Ca2+ greater than K+ greater than Li+ greater than Na+. Co-protoporhyrin behaves essentially as Co-deuteroporphyrin. The results provide further evidence that the efflux of metalloporphyrins from the mitochondria depends on haem-binding ligands of the suspending medium and also on the ionic strength of the incubation medium.

scholarly journals Studies on the efflux of metalloporphyrin from rat-liver mitochondria. Effect of albumin, globin, haemin and haemoglobin

1980 ◽  
Vol 188 (2) ◽  
pp. 459-465 ◽  
Author(s):  
P Husby ◽  
I Romslo
Keyword(s):  
Steady State ◽  
Rat Liver ◽  
Incubation Medium ◽  
Model Compound ◽  
Energy State ◽  
Energy Coupling ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Isolated Rat Liver ◽  
Isolated Rat

The mechanism by which metalloporphyrins escape from mitochondria has been studied in isolated rat-liver mitochondria using Co-deuteroporphyrin as the model compound. During the first 10–15 min of incubation the efflux is about 10% of the total amount of Co-deuteroporphyrin synthesized. The efflux then increases to a second steady-state leve of 25–35% after 30–45 min of incubation. The efflux is inversely correlated to the energy state of the mitochondria. Globin at concentrations less than 0.4 mumol/l enhances the efflux of Co-deuteroporphyrin, but has no effect on the degree of energy coupling or on the rate of Co-deuteroporphyrin synthesis. The effect of globin can be competitively inhibited by adding haemin. Haemin (0.5–1.0 mumol/l) when added to the medium in the absence of globin reduces the efflux of Co-deuteroporphyrin by 20–30%, but has no effect on the metal-chelatase activity. Neither albumin nor haemoglobin increases the efflux of Co-deuteroporphyrin from intact mitochondria. The results suggest that the efflux of metalloporphyrin is regulated in part by the energy state of the mitochondria and in part by the presence of metalloporphyrin-binding ligants and unattached haemin in the incubation medium.

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