SI-PO-0768

Wednesday 15:00, Palau de Congressos, Exhibition Hall  [Display No. 525]

HISTOCHEMICAL AND BIOCHEMICAL ANALYSIS OF DIAPHRAGM. Miyamoto H, Kanemura N, Sasaki H, Tanaka S, Shirahama K, Moriyama H, Suzaki E, Kataoka K, Yoshimura O ; Graduate of Health Sciences. Hiroshima University. Hiroshima. Japan. PURPOSE: Diaphragm is striated muscle bordering between thoracic and abdominal cavities. Diaphragmatic movement is said to contribute to 60%-80% of resting tidal volume, and diaphragm is the most important muscle in performing respiration. RELEVANCE: Physiotherapies, including pre- and post- operative breathing physiotherapy, home oxygen therapy and cardiorespiratory response to exercise, are diversely involved in respiration. In the present study, the difference between diaphragm and other skeletal muscles was investigated through histochemical and biochemical analyses using rat diaphragm. METHODS: Twelve Wistar male rats were used in the present study. The sample muscles were extensor digitorum longus (EDL), soleus (SOL), costal region of diaphragm (DIAcos), and crural region of diaphragm (DIAcru). In addition, the region of DIAcos was divided into 3 of anterior part, middle part and posterior part. Histochemical samples were Pretreated with alkali solution, and that with acid, and were stained Myosin ATPase. Biochemical samples were performed to separate myosin heavy chain (MHC) isoforms, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). RESULTS: EDL was densely stained after pretreatment with alkali solution (pH10.5), suggesting that Type II fibers existed clearly. In SOL, most of the fibers were densely stained after pretreatment with acid solution (pH4.6). In inspiratory muscle of diaphragm, the fibers densely stained were slightly more observed after pretreatment with alkali solution than that with acid solution. Approximately 90% of SOL had MHC I, which indicated the contraction characteristics of Type I fiber. On the contrary, 90% or more of EDL consisted of MHC II. Especially, MHC IIb was contained in approximately 60% of EDL. Diaphragm had 4 MHCs (MHC I, IIa, IId and IIb), and especially had a lot of MHC IId. CONCLUSION: Muscle fibers are histochemically classified into 3 types of Type I, IIA and IIB, and biochemically into 5 types of Type Iα, Iβ, IIA, IID and IIB. These classifications are in agreement with those of MHC, which deeply related to contraction characteristics. When MHCs in SOL, EDL and DIA were detected and analyzed, it was revealed that each muscle had different MHC isoforms. Diaphragm of inspiratory muscle had 4 myosin isoforms, especially a lot of MHC IId controlled by motoneurons of fast-twitch fatigue intermediate type. Diaphragm formed by various muscle fibers is deeply related to its own function. In addition, diaphragm was thought to have the functional system which could deal with various respiratory movements such as slow and shallow breathing in resting period, and the breathing in exercising period which required the ventilation volume several tens as much as that in resting period.