Abstract
In an extensive investigation of the effect of dinitro compounds on tissue respiration and cell division, a point has been reached where it appears desirable to know more about the mechanism by which such compounds stimulate oxidative processes in the cell. We report here some experiments with 4,6 dinitro-o-cresol (DNC)∗ which indicate that dinitro compounds do not act on cell respiration either in the same way as methylene blue and other dyes which are reduced by the cell and re-oxidized by molecular oxygen, 1 or in the same way as dimethyl-p-phenylene diamine, which is reduced by the cell and reoxidized by the indophenol oxidase. 2
When the oxygen consumption of sea urchin eggs is raised by DNC to 400% of the normal, 3 the R.Q. remains unchanged at the normal value of about 0.93. We have found that DNC is not an autoxidizable catalyst for the oxidation of glucose or cysteine, even in the presence of traces of metals or cytolyzed animal tissue. We have also found with rat tissues and eggs of invertebrate marine animals that the action of DNC as a respiratory stimulant can be completely and reversibly blocked by cyanide. Field, Martin and Field report similar results with cyanide on yeast. 4
These facts indicate that DNC acts upon one or more of the cyanide sensitive oxidative chains in the cell. These may be roughly divided into 2 classes: (A) those depending for oxygen activation on Keilin's cyanide sensitive indophenol oxidase, and (B) those in which the substrate is activated by an autoxidizable cyanide sensitive dehydrase. 5 The mechanisms classifiable under (B) do not act through cytochrome, hence a distinction between the 2 classes can be made by studying the effect of DNC on the rate of oxidation or reduction of cytochrome in respiring cells.
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