Histochemical Study on the Flexor Carpi Radialis Muscle of the Male Frog During the Mating Season. II. ATPase activity

Myosin ATPase activity in the flexor carpi radialis muscle (FCRM) fibers of the male frog, Rana japonica, during the mating season was examined histochemically, and the following results were obtained. 1) The fibers in FCRM were divided into two groups, dark and light fibers, by staining after preincubation in acid with the procedure of Guth and Samaha (G-S procedure) for staining of myosin ATPase. On the other hand, after preincubation in alkali, all fibers were stained uniformly and inter mediately, thus the fibers were not divided into groups. 2) When the fibers were stained with the procedure of Padykula and Hermann (P-H procedure) for staining of myosin ATPase, the fibers were divided into two groups, light and dark fibers. 3) In the serial cross sections, the fibers stained dark after the preincubation in acid with G-S procedure were stained relatively light with P-H procedure, and had intermediate activity of succinic dehydrogenase (SDH). In contrast, the fibers stained light after the preincubation in acid with G-S procedure were stained dark with P-H procedure, and were subdivided into two groups, one of which had a high SDH activity and the other a low SDH activity. 4) The fibers stained dark after the preincubation in acid with G-S procedure occupied 21.6% and their mean diameter was 97.2μm., whereas the light fibers occupied 78.4% and their mean diameter was 84.5μm