The distribution of the succinic oxidase system in animal tissues

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Abstract
An adaptation of the methylene blue reduction technique was described for the detn. of succinic dehydrogenase in fresh suspensions. The complete "succinoxidase" system consisting of dehydrogenase, cyto-chrome, and cytochrome oxidase was extremely active in kidney, liver and heart. Brain, testis, skeletal muscle, lung, adrenals, retina, Jensen sarcoma, and Flexner Jobling showed moderate to low activity. Thymus, pancreas, spleen, blood, Philadelphia No. 1 sarcoma and (usually) Walker 256 carcinoma, had practically no activity. The tissues fell roughly into the same order according to succinic dehydrogenase activity and rate of p-phenylene diamine oxidation. In Borne cases the rate of O2 uptake with succinate was limited by low cytochrome content and addition of cytochrome C increased the rate. In all cases cytochrome addition increased the O2 uptake with p-phenylene diamine. The full activity of cytochrome oxidase, as measured by the O2 uptake with p-phenylene diamine in the presence of excess cytochrome, was higher in all tissues than was necessary to account for the whole normal respiration of the tissue. An apparent additive effect of succinate and p-phenylene diamine together on the O2 uptake of brain, testis and other tissues ascribed by early workers to different O2 activating mechanisms for the 2 substrates, was shown to be due to a salt effect of the Na succinate upon the oxidase-cytochrome activity. Blood and haemoglobin promoted the oxidation of p-phenylene diamine; the catalyst, which was independent of cytochrome, was apparently a breakdown product of haemoglobin produced by the diamine.