Abstract
The aim of this work is to study whether an unbalanced dietary protein intake may cause changes in nitrogen content of the hepatic mitochondria. Previous observations(1) demonstrated that in normal rats fed protein deficient diet or fasted, some enzymatic activities of the hepatic mitochondria/mg of mito-chondrial nitrogen varied inversely with protein intake. These data led to the hypothesis that protein deficiency may cause a reduction of nitrogenous material in mitochondria and that consequently it may not be always advisable to relate enzymatic activity of mitochondria, to their nitrogen content, as is generally done. In our work mitochondria were counted to study the effect of fasting and of hypo- and hyperprotein diets on nitrogen content of each mitochondrion and on concentration of several enzymes/single mitochondrion and/mg of mitochondrial nitrogen.
Materials and methods. Male Wistar rats about 90 days olld were fed 3 different food mixtures (Table I). All animals received a weekly supplement of 350 units of Vit. A. At end od experiment, the animals were fasted 12 hours and decapitated. The liver was quickly removed and the homogenate prepared at 0°. IIitochondria were separated from homogenate according to Schneider (2) in a solution of 0.25 31 sucrose and 0.01 31 ethylenediaminotetraacetic acid (EDTA), and washed 3 times in the same solution. The following activities were investigated: cytochrome-oxidase (3), succinic-oxidase (3), beta-hydroxybutyric-oxidase (3), ATPase (4). Nitrogen was determined by Nessler's reagent. Mitochondria were counted in a counting chanilwr using a phase-contrast microscope.
Results. Table I1 shows results. The hypoprotein diet caused marked reduction of nitrogen content without conspicuous decrease in enzymatic activities of single mitochondria. b'asting caused a very distinct decrease of nitrogen content with simultaneous decrease of enzymatic activities of single mitochondria.
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