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(5)X TGF-1 Ettct ofIGF on lnh ibLio n ofmyotube ibrmation by Xray radiation:1 Ju MIYAK OS HI ( PrOfessor of Hsaki UniversityTomonori Saki ai, Takanori Ueda and Jutti MIYAKOSHI Department ofRadiological Siences,Dsion ofMedical Life SciencesGraduate School of Health Sciences,Hirosaki Universitymivakosh@cc.hirosaki.acoip

: () : ()INTRODUCTION:Skeletal muscle is relatively stable tissue composed of differentiated musclefibers.HOwevet growth and repalr of skeletal lnuscle are carried out in response to damage Orstretch. Skeletal muscle is relatively resistant to X ray radiation, but the formation ofmultinucleated myotubes is delayed or suppressed by Xray irradiation of myoblastsl),2).Expression of insuhnlike growth factOr(IGF1)increases during generation and regeneration ofskeletal muscle3).The overexpression ofIGF l result in myofiber hypertrophy 4).PIJRPOSE:In this study we investigated whether IGF l improve the delay or suppression ofmyotube formation induced by X ray irradiation.MATERIRLS AND METHODS:Mouse derived myoblast C2C12 were seeded at a density of 4 104cells/cm2 0n a 24well celldesk plate(SumitOmo Bakelite).Atter an overnight culture in DMEMmedium supplemented with 10%feral bOvine serum(FBS),X ray irradiation at 2 or 4 Gy using anXray generator O BR1520R; Hitachi Medical Corporation, at 150 kV and 20 mA with analuminum lter Of O.5 mm and a copper ilter Ofo.lmm(90 cGy/min))was conducted,and then themediuln was replaced with DMEM medium with 20/O FBS and the culture was continued for 6 daysto induce direrentiationo Differentiation of cells into myocytes and myotubes was identified bynuorescence ilnmunostaining with an anti myosin (skeletal muscle) monOclonal antibody

(Histofine).RESULTS i The results of irnmunOstaining are shown belolM Decreased myOtube formatiOn was

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CONCLUSION : The decrease in the number of differentiated cells and reduction in myotubeformation induced by X'ray radiation of 2 Gy were inhibited by IGF-1. The X-ray irradiation at 2 Gyis used in multi'fractionated irradiation in radiotherapy, and therefore IGF-I may be useful forreduction of radiation damage.References1) Santini MT et al., Int J. Radiat Biol b8 : 469-474 tggO).2) Ikeda S et al., Int J Radiat Biol 76: 408-4LI (2000).3) Florini JR et al., Endomine Rev 1T: 481-517 tggA).

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