Despite anorexia, cancer development is frequently accompanied by an increase of energy expenditure. Considering the pivotal role played by brown adipose tissue (BAT) in the energy metabolism of small mammals, we investigated the functional and compositional modification in BAT of anorexic tumor-bearing (Yoshida sarcoma) and pair-fed control rats. BAT thermogenic activity (assessed by maximal mitochondrial GDP binding) was 1.8-fold greater in tumor-bearing rats than in controls, while the thermogenic capacity (assessed by measurement of uncoupling protein) was unchanged. This suggests that tumor bearing had induced an unmasking of uncoupling protein sites. BAT hypertrophy and hyperplasia, characteristic of full-fledged BAT activation, did not occur. The mitochondrial oxidative capacity of BAT (assessed by cytochrome c oxidase activity) was 1.6-fold lower in tumor-bearing than in control rats. The main compositional modification observed in BAT of tumor-bearing rats was an increase in the saturation of cardiolipin fatty acids. These results suggest that the BAT stimulation induced by tumor bearing after 10 days is almost exclusively functional and that the tissue development is limited, probably by anorexia. However, a suppressive effect of anorexia inhibition by tumor bearing cannot be excluded.
A sensitive procedure is described for the simultaneous determination of vitamin E and coenzyme Q homologues and ␣ -tocopherol oxidation products using twoisocratic step high pressure liquid chromatography (HPLC) and electrochemical detection in the oxidative mode. Zinccatalyzed reduction in a post-column reactor allows the detection of ␣ -tocopherolquinone, epoxy-tocopherolquinone, and ubiquinones. This technique was used to quantify lipophilic antioxidants in the liver tissue of rats treated or not with ␣ -tocopherolquinone and in a plant oil. ␣ -Tocopherolquinone and its epoxide derivatives, formed from ␣tocopherol during iron-catalyzed phospholipid peroxidation, were also determined in a liposome suspension. The high selectivity and sensitivity of the coulometric detection system enabled use of low oxidation potentials giving little baseline noise, while a fast isolation procedure and quantitative recoveries of all oxidized and reduced forms made it possible to measure a high ubiquinol/ubiquinone ratio in liver tissue. Administration of ␣ -tocopherolquinone to rats did not alter the antioxidant status of the liver, despite strong accumulation of both this quinone and its reduced form, ␣ -tocopherolhydroquinone. These results indicate the presence of an efficient reductase and suggest that it could contribute to the protection of cellular membranes from oxidative stress.-Leray, C., M. D. Andriamampandry, M. Freund, C. Gachet, and J-P. Cazenave. Simultaneous determination of homologues of vitamin E and coenzyme Q and products of ␣ -tocopherol oxidation.
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