scholarly journals 2,3-Butanedione monoxime unmasks Ca2+-induced NADH formation and inhibits electron transport in rat hearts

2000 ◽  
Vol 279 (4) ◽  
pp. H1839-H1848 ◽  
Author(s):  
Russell C. Scaduto ◽  
Lee W. Grotyohann
Keyword(s):  
Electron Transport ◽  
Atp Hydrolysis ◽  
Adenine Nucleotide ◽  
Liver Mitochondria ◽  
Submitochondrial Particles ◽  
Rat Hearts ◽  
Butanedione Monoxime ◽  
Low Levels ◽  
Perfused Hearts ◽  
Adenine Nucleotide Transport

We used 2,3-butanedione monoxime (BDM) to suppress work by the perfused rat heart and to investigate the effects of calcium on NADH production and tissue energetics. Hearts were perfused with buffer containing BDM and elevated perfusate calcium to maintain the rates of cardiac work and oxygen consumption at levels similar to those of control perfused hearts. BDM plus calcium hearts displayed higher levels of NADH surface fluorescence, indicating calcium activation of mitochondrial dehydrogenases. These hearts, however, displayed 20% lower phosphocreatine levels. BDM suppressed the rates of state 3 respiration of isolated mitochondria. Uncoupled respiration was suppressed to a lesser degree, and the state 4 respiration rates were not affected. Double-inhibitor experiments with liver mitochondria using BDM and carboxyatractyloside (CAT) were used to identify the site of inhibition. BDM at low levels (0–5 mM) suppressed respiration. In the presence of CAT at levels that inhibit respiration by 60%, low levels of BDM were without effect. Because these effects were not additive, BDM does not inhibit adenine nucleotide transport. This was supported by an assay of adenine nucleotide transport in liver mitochondria. BDM did not inhibit ATP hydrolysis by submitochondrial particles but strongly suppressed reversed electron transport from succinate to NAD+. Oxidation of NADH by submitochondrial particles was inhibited by BDM but oxidation of succinate was not. We conclude that BDM inhibits electron transport at site 1.

scholarly journals Oxidative phosphorylation. The effect of anions on the inhibition by triethyltin of various mitochondrial functions, and the relationship between this inhibition and binding of triethyltin

1972 ◽  
Vol 127 (1) ◽  
pp. 51-59 ◽  
Author(s):  
M. S. Rose ◽  
W. N. Aldridge
Keyword(s):  
Electron Transport ◽  
Oxygen Uptake ◽  
Atp Hydrolysis ◽  
Atp Synthesis ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Hydroxide Ion ◽  
Mitochondrial Functions ◽  
Relationship Of ◽  
The Relationship

1. The binding of triethyltin to rat liver mitochondria is unaffected by the nature of the predominant anion in the incubation medium. 2. With chloride, bromide or iodide as the predominant anion, ATP synthesis linked to the oxidation of pyruvate or succinate and ATP hydrolysis stimulated by 2,4-dinitrophenol are much more sensitive to triethyltin than they are when nitrate or isethionate is the predominant anion. 3. When nitrate or isethionate is the predominant anion, oxygen uptake stimulated by 2,4-dinitrophenol is not inhibited by triethyltin. 4. In the presence of nitrate or isethionate anions, inhibition of ATP synthesis is directly related to the binding of triethyltin to mitochondria. 5. The relationship of the above effects to the anion–hydroxide ion exchange mediated by triethyltin and the relevance of this to published arrangements for coupling of electron transport to ATP synthesis are discussed.

scholarly journals The pathway of inorganic-phosphate efflux from isolated liver mitochondria during adenosine triphosphate hydrolysis

1980 ◽  
Vol 192 (3) ◽  
pp. 821-828 ◽  
Author(s):  
David D. Tyler
Keyword(s):  
Atpase Activity ◽  
Large Amplitude ◽  
Atp Hydrolysis ◽  
Adenine Nucleotide ◽  
Sucrose Solution ◽  
Adenine Nucleotides ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Nucleotide Exchange ◽  
Major Activity

1. The distribution of Pi between mitochondria and suspending medium during uncoupler-stimulated hydrolysis of ATP by rat liver mitochondria [Tyler (1969) Biochem. J.111, 665–678] has been reinvestigated, by using either mersalyl or N-ethylmaleimide as inhibitors of Pi transport and either buffered sucrose/EDTA or LiCl/EGTA solutions as suspending medium. More than 75% of the total Pi liberated was retained in mitochondria treated with either inhibitor at all ATP concentrations tested (0.2–2.5mm). With low ATP concentrations and mersalyl-treated mitochondria incubated in sucrose/EDTA, virtually all the Pi liberated was retained in the mitochondria. 2. Larger amounts of Pi appeared in the suspending medium during ATPase activity, despite the presence of N-ethylmaleimide, when LiCl/EGTA was used as suspending medium compared with sucrose/EDTA. Two sources of this Pi were identified: (a) a slow efflux of Pi from mitochondria to suspending medium despite the presence of N-ethylmaleimide; (b) a slow ATPase activity insensitive to carboxyatractyloside, which was stimulated by added Mg2+, partially inhibited by oligomycin or efrapeptin and strongly inhibited by EDTA. 3. It is concluded that liver mitochondria preparations contain two distinct forms of ATPase activity. The major activity is associated with coupled mitochondria of controlled permeability to adenine nucleotides and Pi and is stimulated strongly by uncoupling agents. The minor activity is associated with mitochondria freely permeable to adenine nucleotides and Pi, is unaffected by uncoupling agents and is activated by endogenous or added Mg2+. 4. When mitochondria treated with mersalyl were incubated in buffered sucrose solution, almost all the Pi liberated was recovered in the suspending medium, unless inhibitors of Pi-induced large-amplitude swelling such as EDTA, EGTA, antimycin, rotenone, nupercaine or Mg2+ were added. Thus the loss of the specific permeability properties of the mitochondrial inner membrane associated with large-amplitude swelling also influences the extent of Pi retention during ATPase activity. 5. The results confirm the previous conclusion (Tyler, 1969) that the Pi transporter provides the sole pathway for Pi efflux during uncoupler-stimulated ATP hydrolysis by mitochondria. It is concluded that more recent hypotheses concerning the influence of Mg2+ on mersalyl inhibition of the Pi transporter [Siliprandi, Toninello, Zoccaroto & Bindoli (1975) FEBS Lett. 51, 15–17] and a postulated role of the adenine nucleotide exchange carrier in Pi efflux [Reynafarje & Lehninger (1978) Proc. Natl. Acad. Sci. U.S.A.75, 4788–4792] are erroneous and should be discarded.

Adenine nucleotide transport in sonic submitochondrial particles. Kinetic properties and binding of specific inhibitors

1977 ◽  
Vol 460 (2) ◽  
pp. 331-345 ◽  
Author(s):  
Guy J.M. Lauquin ◽  
Christian Villiers ◽  
Jan W. Michejda ◽  
Lilla V. Hryniewiecka ◽  
Pierre V. Vignais
Keyword(s):  
Adenine Nucleotide ◽  
Kinetic Properties ◽  
Submitochondrial Particles ◽  
Adenine Nucleotide Transport ◽  
Specific Inhibitors
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