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Functional aspects of megamitochondria isolated from hydrazine- and ethanol-treated rat livers
T Wakabayashi1, M A Teranishi, M Karbowski
1Department of Cell Biology and Molecular Pathology, Nagoya University School of Medicine, Nagoya, Japan. twakaba@tsuru.med.nagoya-u.ac.jp
Abstract:
It is essential to analyze functions of megamitochondria (MG) to elucidate the mechanism of the formation of MG induced under various pathological conditions. The MG fraction obtained by a routine isolation procedure for normal mitochondria always consists of a mixed population of mitochondria enlarged to various degrees and also normal-sized ones. The purpose of the present study is to answer the question of whether or not data obtained from the MG fraction consisting of such a heterogeneous population of mitochondria with respect to their sizes really reflect functions of MG. In the present study mitochondria were obtained from the livers of rats treated with a 1% hydrazine diet for 8 days and those given 32% ethanol in drinking water for up to 2 months using various isolation procedures. Results obtained are summarized as follows: (i) mitochondria enlarged to various degrees and normal-sized ones are sometimes connected with each other by a narrow stalk in the hepatocyte of hydrazine-treated animals, and such connections are maintained to some extent when mitochondria are isolated; and (ii) mitochondria obtained from experimental animals by a routine isolation procedure for mitochondria ((700-7000)gR2"') and those obtained by alternative isolation procedure yielding the heavy ((500-2000)gR2"') and light ((2000-7000)gR2"') fractions show some functional similarities: decreases in the content of cytochrome a + a3; decreases in oxygen consumptions and phosphorylating abilities; decreases in monoamine oxidase and cytochrome c oxidase activities; lowered membrane potential of mitochondria; decreases in the rate of the generation of reactive oxygen species. These results may suggest that mitochondria enlarged to various degrees and normal-sized ones are functionally similar to each other and that the MG fraction obtained by a routine isolation procedure for normal mitochondria can be applied to the study of the function of MG.
Insights
Analyzing megamitochondria (MG) function is crucial. This study found that enlarged and normal mitochondria share functional similarities, validating routine isolation methods for MG research.
Area of Science:
- Cell Biology
- Mitochondrial Biology
- Pathology
Background:
- Megamitochondria (MG) formation is observed in various pathological conditions.
- Understanding MG function is key to elucidating disease mechanisms.
- Current MG isolation procedures yield heterogeneous populations of enlarged and normal-sized mitochondria.
Purpose of the Study:
- To determine if functional data from heterogeneous MG fractions accurately represent MG function.
- To investigate the functional characteristics of enlarged versus normal-sized mitochondria within pathological contexts.
Main Methods:
- Mitochondria were isolated from rat livers using standard and alternative procedures.
- Rats were treated with hydrazine diet or ethanol in drinking water to induce pathological conditions.
- Functional analyses included measuring cytochrome content, oxygen consumption, phosphorylating abilities, enzyme activities (monoamine oxidase, cytochrome c oxidase), membrane potential, and reactive oxygen species generation.
Main Results:
- Enlarged and normal-sized mitochondria were observed connected by stalks in hepatocytes and partially maintained upon isolation.
- Both routine and alternative isolation procedures yielded fractions with functional similarities.
- Key functional deficits observed included decreased cytochrome a + a3, oxygen consumption, phosphorylating ability, enzyme activities, membrane potential, and ROS generation.
Conclusions:
- Enlarged and normal-sized mitochondria exhibit functional similarities.
- Routine mitochondrial isolation procedures are suitable for studying megamitochondria (MG) function.
- The findings support the use of standard isolation techniques for analyzing MG in pathological conditions.
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