The intensity of succinate oxidation in surviving liver tissue.

IN previous studies [Rosenthal, 1935] on the metabolism of surviving rat liver the question arose as to the extent to which the great differences in the respiration of liver tissues of individual rats are due to differences in the amount of "respiration ferment" (indophenol oxidase-cytochrome system). Measurement of the speed of oxidation of p-phenylenediamine-the direct determination of the amount of indophenol oxidase-does not give satisfactory results in the case of tissue slices. The autoxidation of the base interferes with the accuracy of the measurement; furthermore, the precipitate 'of dyestuff which is formed on the surface of the slices seems to injure the tissue. On the other hand, the measurement of the oxidation of succinate by tissue slices provides a suitable method for the determination of the minimum amount of indophenol oxidase in the organ, since succinate is oxidized by molecular 02 through the indophenol oxidase-cytochrome system. The speed of succinate oxidation by slices of rat liver is extremely high, much higher than one might expect from the results of Krebs [1933], Edson [1936] and Califano [1937]. The speed of this oxidation exceeds the speed of the oxidation of other substrates by several hundred % and remains at this level for a long period of time. There is relatively little fluctuation in the values obtained from different livers. In the present paper the conditions under which the maximum speed of succinate oxidation can be measured in slices of rat liver will be shown. The values for the amount of "respiration ferment" in different livers obtained by this method will be compared with the values of the respiration with and without addition of other substrates.