Succinic Dehydrogenase System Research Articles

Tetrazolium stains for diphosphopyridine nucleotide (DPN) diaphorase and triphosphopyridine nucleotide (TPN) diaphorase in animal tissue.

SummaryMethods for the specific staining for DPN diaphorase and TPN diaphorase in frozen sections of fresh tissue are presented. The staining patterns of rat kidney are highly reproducible and are distinctly different for each of the 2 diaphorases and for the succinic dehydrogenase system.

The effect of a-estradiol, some of its esters and estrone on the respiration of tissue homogenates.

MEYER et al. (1948) showed that certain natural and synthetic estrogens in concentrations of 0.2 to 3 × 10−4 M inhibit tissue respiration by attacking the iron compounds in the cytochrome system. The portion of the estrogenic molecule responsible for this inhibition was traced to the free phenolic groups of these compounds. Case and Dickens (1948) described some synthetic estrogens which inhibit the succinoxidase by acting on the cytochrome portion, some which inhibit by acting on the succinic dehydrogenase system, and still others which inhibit the over-all oxidation of succinate but which act neither on the cytochrome oxidase nor the succinic dehydrogenase. Data are herein reported which suggest a-estradiol, some of its esters, and estrone in a concentration of 5 × 10−5 M inhibit oxidation of substrates whose oxidative systems are coenzyme linked but do not inhibit the succinoxidase system. MATERIALS AND METHODS

Effect of method of homogenization of beef muscle tissue on activity of succinic dehydrogenase system.

The succinic dehydrogenase activity of beef muscle determined after different methods of homogenization of the tissue was investigated. The amount of beef muscle needed for a representative sample was too large to be conveniently used with the Potter-Elvehjem homogenizer; however, the samples could be prepared for assay by homogenizing in a Waring blendor, provided that the homogenization time is held to a minimum. This was evidenced from studies which showed that homogenizing the minced beef tissues in a Waring blendor for 1 minute or homogenizing Latapie minces for 1/2 minute resulted in a greater succinic dehydrogenase activity than that obtained when the tissues were homogenized for longer periods. Other experiments with rat tissues showed that the enzyme activity of rat muscle homogenized in the Waring blendor for 1 minute, in a Potter-Elvehjem homogenizer, or ground with sand was essentially the same.

Enzyme inhibition in relation to chemotherapy.

Summary1. The effect of enzyme concentration on the inhibition produced by certain inhibitors of the succinic dehydrogenase system has been experimentally determined. The inhibitors studied were malonate, itaconate, oxalacetate, quinone and cupric ion.2. The reaction between succinic dehydrogenase and copper or quinone was not immediate but required 30 to 40 minutes when the amount of inhibitor was just sufficient to produce complete inhibition.3. The effect of the strengths of binding of the inhibitor with the enzyme on the percent inhibition produced is shown to be related to the enzyme concentration.4. An expression has been developed which relates the velocity of reaction to enzyme concentration in enzyme-inhibitor systems.5. The results are discussed in relation to the chemotherapy of cancer. It is pointed out that the selective inhibition of an enzyme not unique to cancer tissue is theoretically possible.

THE METABOLISM OF THE KIDNEY IN EXPERIMENTAL RENAL HYPERTENSION

These investigations are part of an attempt to study and interpret the intermediary metabolism of the kidneys in experimental renal hypertension. Hypertension was produced in dogs by the clamping procedure of Goldblatt and associates or by the silk perinephritis method of Page. Enzymatic studies were made by means of Warburg's manometric method. Cytochrome c was in addition determined spectrophotometrically. Tissue slices, homogenized tissue, and tissue extracts were used. A study of the cytochrome c concentration and the activities of the cytochrome oxidase and succinic dehydrogenase systems of kidneys from normal dogs and dogs with experimental renal hypertension was made. It was found that the cytochrome c concentration and the activities of the cytochrome oxidase and succinic dehydrogenase systems were markedly lower in the kidney slices and in the tissue suspensions from hypertensive dogs. Tissue suspensions and extracts of kidneys from hypertensive dogs showed an inhibitory effect on the activity of the cytochrome oxidase and succinic dehydrogenase, and the amine oxidase systems. Renin preparations also showed a marked inhibitory effect on the activities of cytochrome oxidase, succinic dehydrogenase, l-amino acid oxidase, and amine oxidase systems. A significant increase was found in the kidney of dogs whose other kidney had been removed or subjected to Goldblatt's or Page's technique in the activities of the cytochrome-cytochrome oxidase system, the succinic dehydrogenase system, and in the concentration of nucleotide-bound phosphorus, of flavin-adenine dinucleotide, and of the nicotinamide-adenine dinucleotides (coenzymes I and II). From the results of these studies it can be concluded that an increase in the concentration and activity of the respiratory enzymes precedes hypertrophy of the kidney. This can be explained by the assumption that an increase in the activity of the respiratory biocatalysts acts as a stimulus for cell growth and multiplication.