Abstract
It has been known since the early works on the respiratory systems of animal tissues (1-5), that cytochrome oxidase operates as the terminal system of respiratory chain and the oxidative activity is completely inhibited by cyanide as well as by azide. Stotz et al. (6) and Smith (7) reported that ascorbic acid is oxidized by cytochrome oxidase system in animal tissues.
In the course of the studies on the tissue respiration of rat intestine, it was found that respiration of small intestinal homogenate of rats without substrates was not inhibited by cyanide, and when ascorbic acid or cytochrome c and ascorbic acid were added as substrates, the respiration increased by 20 to 40 per cent in the presence of cyanide (8). This accelerating effect of cyanide on the respiration did not take place in other tissues of rats and various tissues of guinea pigs. Therefore, it can be said that this may be characteristic of rat small intestine. The purpose of the present work is to clarify the cause of this phenomenon.
