A histochemical study of the red and white muscle fibers Part III. Activity of the diphosphopyridine nucleotide diaphorase and triphosphopyridine nucleotide diaphorase in muscle fibers

From the histochemical study of DPN and TPN diaphorase on the striated muscles of the cats, the following results were obtained. 1. M. gastrocnemius, which belongs to the white muscle by naked eye, consists of three types of muscle fibers distinguished by the DPN diaphorase staining: namely, the small muscle fibers, i. e., the red muscle fibers show a moderate activity, being stained pink, while the large muscle fibers, i. e., the white muscle fibers show a low activity, being stained faint pink. The. third type of muscle fibers: namely, the medium fibers are stained pale pink and show the enzymatic activity intermediate between the red and white muscle fibers. 2. M. soleus, belonging to the red muscle by naked eye, consists of three types of fibers distinguished by the DPN-diaphorase staining, i. e., the red muscle fibers are stained pink, medium fibers pale pink, and a few white muscle fibers faint pink. The diameters of these three types of muscle fibers in M. soleus are almost the same. 3. From the staining pattern of TPN-diaphorase in M. gastrocnemius and M. soleus, the three types of muscle fibers can be distinguished by TPN-diaphorase activity, namely, the red muscle fibers show a high TPN-diaphorase activity, being stained purple, while, the white muscle fibers a low activity, being stained pale pink. The medium fibers are stained pink and show a moderate enzymatic activity intermediate between the red and white muscle fibers. 4. The TPN-diaphorase activity is higher than the DPN-diaphorase activity in the striated muscle, but it is less active than the TPN-diapborase activity in the kidney. However, the activity of DPN-diaphorase in the striated muscle is quite lower than that of the kidney.