Ethanol oxidation in systems containing soluble and mitochondrial fractions of rat liver

In the present study, we have investigated gender differences in rat liver mitochondrial oxidative metabolism. Total mitochondrial population (M) as well as the heavy (M1), medium (M3), and light (M8) mitochondrial fractions obtained by means of differential centrifugation steps at 1,000, 3,000, and 8,000 g, respectively, were isolated. Electron microscopic analysis was performed and mitochondrial protein content and cardiolipin levels, mitochondrial O2 flux, ATP synthase activity, mitochondrial membrane potential, and mitochondrial transcription factor A (TFAM) protein levels were measured in each sample. Our results indicate that mitochondria from females have higher protein content and higher cardiolipin levels, greater respiratory and phosphorylative capacities, and more-energized mitochondria in respiratory state 3. Moreover, protein levels of TFAM were four times greater in females than in males. Gender differences in the aforementioned parameters were more patent in the isolated heavy M1 and M3 mitochondrial fractions. The present study demonstrates that gender-related differences in liver mitochondrial function are due mainly to a higher capacity and efficiency of substrate oxidation, likely related to greater mitochondrial machinery in females than in males, which is in accord with greater mitochondrial differentiation in females.

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Pyrimidine reducing enzymes of rat liver

Canadian Journal of Biochemistry ◽

10.1139/o76-026 ◽

1976 ◽

Vol 54 (2) ◽

pp. 178-184 ◽

Cited By ~ 14

Author(s):

Ronald O. Hallock ◽

Esther W. Yamada

Keyword(s):

Carbon Dioxide ◽

Rat Liver ◽

Gel Electrophoresis ◽

Marker Enzyme ◽

Good Separation ◽

Cytosol Fraction ◽

Radioactive Carbon ◽

Mitochondrial Fractions ◽

Optimum Ph ◽

Rat Liver Cells

Dihydrouracil dehydrogenase (NADP+) (EC 1.3.1.2) was partially purified from the cytosol fraction of rat liver and fractionated by disc gel electrophoresis. A major and minor band were visualized by staining for enzyme activity. The substrate specificity of these bands was investigated. It was found that both bands were two to three times more active with dihydrothymine as substrate than with dihydrouracil in the presence of NADP+ and the optimum pH of 7.4.Mitochondrial fractions containing most of the NADH-dependent uracil reductase of rat liver cells were fractionated by centrifugation in sucrose density gradients. Two procedures involving linear or discontinuous gradients were used. By both, good separation of NADH- and NADPH-dependent reductases was achieved. Marker enzyme studies supported the view that the NADH-dependent enzyme is located principally in mitochondria whereas the NADPH-dependent enzyme is mainly in plasma and endoplasmic reticulum membranes. For the NADH-dependent reductase the apparent Km for thymine at pH 7.4 was 1.39 times that found for uracil whereas for the NADPH-dependent enzyme the apparent Km values were similar for the two substrates at this pH.Dihydrouracil was the principal product isolated by paper chromatography from the reaction mixture containing a partially purified fraction of mitochondria, uracil and NADH at pH 7.4. This fraction also catalyzed the formation of radioactive carbon dioxide from [2-14C]uracil. The proportion of CO2 formed by the mitochondria was about 10% of that formed by the original homogenate.

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