Uncoupling of oxidative phosphorylation in rat liver mitochondria by chloroethanols

Hari K. Bhat, Gregory K. Asimakis, Ghulam Ansari

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Chloroethanols are toxic chemicals used in industry and also formed as a result of the metabolism of several widely used halogenated hydrocarbons. The effect of 2-chloroethanol (CE), 2,2-dichloroethanol (DCE) and 2,2,2-trichloroethanol (TCE) on rat liver mitochondrial respiration was studied. Rat liver mitochondria were isolated in a medium consisting of 250 mM sucrose, 10 mM Tris-HCl and 1 mM EDTA (pH 7.4). Mitochondrial respiration was determined with an oxygen electrode at 30°C and the polarographic buffer consisted of 250 mM mannitol, 10 mM KC1, 10 mM K2HPO4, 5 mM MgCl2, 0.2 mM EDTA and 10 mM Tris-HCl (pH 7.4). With succinate as the respiratory substrate and using chloroethanols (150 mM), CE stimulated respiration by 28.2 ± 6.5% and DCE by 202.7 ± 8.2% while TCE inhibited mitochondrial respiration (>95%). The effect of change in the concentration of chloroethanols on mitochondrial respiration was also studied. CE showed maximum stimulation at 600 mM (97.6%), DCE at 150 mM (202.6%) and TCE at 30 mM (313.6%). Respiratory stimulation was independent of mitochondrial protein concentration. Chloroethanols (optimal concentrations for respiratory stimulation with succinate) inhibited mitochondrial respiration when glutamate-malate was used as the respiratory substrate. Estimation of adenosine triphosphate (ATP) showed that chloroethanols inhibited the synthesis of ATP. These results indicate that chloroethanols stimulate mitochondrial respiration by uncoupling oxidative phosphorylation and that the uncoupling potency is proportional to the extent of chlorination at the β-position of haloethanol.

Original languageEnglish
Pages (from-to)203-211
Number of pages9
JournalToxicology Letters
Volume59
Issue number1-3
DOIs
StatePublished - 1991

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Mitochondria
Liver Mitochondrion
Oxidative Phosphorylation
Liver
Rats
Respiration
Succinic Acid
Edetic Acid
Adenosine Triphosphate
Halogenated Hydrocarbons
Magnesium Chloride
Poisons
Chlorination
Mitochondrial Proteins
Mannitol
Substrates
Metabolism
Sucrose
Glutamic Acid
Buffers

Keywords

  • Chloroethanols
  • Liver mitochondria
  • Uncoupling of oxidative phosphorylation

ASJC Scopus subject areas

  • Toxicology

Cite this

Uncoupling of oxidative phosphorylation in rat liver mitochondria by chloroethanols. / Bhat, Hari K.; Asimakis, Gregory K.; Ansari, Ghulam.

In: Toxicology Letters, Vol. 59, No. 1-3, 1991, p. 203-211.

Research output: Contribution to journalArticle

Bhat, Hari K. ; Asimakis, Gregory K. ; Ansari, Ghulam. / Uncoupling of oxidative phosphorylation in rat liver mitochondria by chloroethanols. In: Toxicology Letters. 1991 ; Vol. 59, No. 1-3. pp. 203-211.
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AB - Chloroethanols are toxic chemicals used in industry and also formed as a result of the metabolism of several widely used halogenated hydrocarbons. The effect of 2-chloroethanol (CE), 2,2-dichloroethanol (DCE) and 2,2,2-trichloroethanol (TCE) on rat liver mitochondrial respiration was studied. Rat liver mitochondria were isolated in a medium consisting of 250 mM sucrose, 10 mM Tris-HCl and 1 mM EDTA (pH 7.4). Mitochondrial respiration was determined with an oxygen electrode at 30°C and the polarographic buffer consisted of 250 mM mannitol, 10 mM KC1, 10 mM K2HPO4, 5 mM MgCl2, 0.2 mM EDTA and 10 mM Tris-HCl (pH 7.4). With succinate as the respiratory substrate and using chloroethanols (150 mM), CE stimulated respiration by 28.2 ± 6.5% and DCE by 202.7 ± 8.2% while TCE inhibited mitochondrial respiration (>95%). The effect of change in the concentration of chloroethanols on mitochondrial respiration was also studied. CE showed maximum stimulation at 600 mM (97.6%), DCE at 150 mM (202.6%) and TCE at 30 mM (313.6%). Respiratory stimulation was independent of mitochondrial protein concentration. Chloroethanols (optimal concentrations for respiratory stimulation with succinate) inhibited mitochondrial respiration when glutamate-malate was used as the respiratory substrate. Estimation of adenosine triphosphate (ATP) showed that chloroethanols inhibited the synthesis of ATP. These results indicate that chloroethanols stimulate mitochondrial respiration by uncoupling oxidative phosphorylation and that the uncoupling potency is proportional to the extent of chlorination at the β-position of haloethanol.

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