Passive transport of 5,5-dimethyl-2, 4-oxazolidinedione into beef heart mitochondria
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Abstract:
5,5-Dimethyl-2,4-oxazolidinedione is used to estimate intracellular pH. The mechanism of transport of this compound into beef heart mitochondria was investigated to assess the validity of its use for the measurement of intramitochondrial pH. This compound and (14)C-labeled carboxy dextran were simultaneously used to determine the intra- and extramitochondrial compartments and the distribution of the compound, which was passively transported into resting, respiring, and simultaneously respiring and phosphorylating mitochondria. The transport of the compound was neither associated with electron transport nor with oxidative phosphorylation.
Insights
5,5-Dimethyl-2,4-oxazolidinedione measures intracellular pH by passive transport into mitochondria. Its uptake is independent of electron transport and oxidative phosphorylation, validating its use for intramitochondrial pH assessment.
Area of Science:
- Biochemistry
- Cell Biology
- Mitochondrial Physiology
Background:
- 5,5-Dimethyl-2,4-oxazolidinedione is a commonly used weak acid for estimating intracellular pH.
- Accurate measurement of intramitochondrial pH is crucial for understanding mitochondrial function.
- The transport mechanism of this pH indicator into mitochondria requires elucidation to confirm its validity.
Purpose of the Study:
- To investigate the transport mechanism of 5,5-Dimethyl-2,4-oxazolidinedione into beef heart mitochondria.
- To assess the validity of using this compound for measuring intramitochondrial pH under various physiological conditions.
Main Methods:
- Simultaneous incubation of beef heart mitochondria with 5,5-Dimethyl-2,4-oxazolidinedione and (14)C-labeled carboxy dextran.
- Determination of intra- and extramitochondrial compartments and compound distribution.
- Assessment of transport in resting, respiring, and phosphorylating mitochondria.
Main Results:
- 5,5-Dimethyl-2,4-oxazolidinedione passively distributes across the mitochondrial membrane.
- Mitochondrial uptake of the compound is not linked to electron transport.
- The transport mechanism is independent of oxidative phosphorylation.
Conclusions:
- The passive transport of 5,5-Dimethyl-2,4-oxazolidinedione into mitochondria is confirmed.
- Its uptake mechanism is not influenced by mitochondrial respiratory or phosphorylation states.
- These findings support the validity of using 5,5-Dimethyl-2,4-oxazolidinedione for accurate intramitochondrial pH measurements.