Mitochrondria from embryonic tissues of the chick. 2. Metabolic activities

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Abstract
A manometric study has been made of the oxidative metabolism of mitochondria from 5-day chick embryos. The apparent oxidation of tricarboxylic acid-cycle intermediates and catalysis of the oxidation of pyruvate by fumarate and other intermediates, as well as the inhibition of the respiration by 5 n[image]-malonate, suggest that the tricarboxylic acid cycle was operative in these particles. DL-Lactate was not oxidized. The respiration in the presence of fumarate plus pyruvate was dependent on addition of adenosine triphosphate and Mg2+ ions. The respiration with various substrates was abolished by 0.5 m[image]-cyanide. The mitochondria readily oxidized D-[beta]-hydroxybutyrate and fatty acids could not be demonstrated. Experiments with preparations from subdivided embryos suggested that mitochondria from individual tissues would present a picture similar to that outlined above. Manometric observations with mitochondrial fractions isolated in a salt medium from livers of embryos and chicks of various ages suggested that, under these conditions, the older the chick the more likely it is that fatty acid oxidation can be shown. Oxidation of acetate by mitochondrial fractions from livers of 16-18-day chick embryos has been studied manometrically. Twice, particles isolated in a sucrose medium showed acetate oxidation only after preincubation in the absence of added substrate; subsequent preparations of this type showed it without pre-incubation. When particles isolated in a salt medium were suspended finally, before addition to the manometer vessels, in media containing magnesium sulphate and adenosine triphosphate, the apparent oxidation of acetate was much less than when they were finally suspended in media free from these substances. This was despite the presence of the two substances during the manometric observations in both cases.