Ultrastructural Pathological Study Of Medial Rectus Muscle In Cat Model With Exotropia After The Injection Of IGF-I

Objective To observe the ultrastructuralchanges of medial rectus muscle in cat model with exotropia after the injectionof IGF-I and to explore the fesibility of IGF-I in treatment of concomitant exotropia.Methods 36 cats that were in the 4-6 weeks were selected for surgery to create anexotropia model.All they were randomly divided into experimental,sterile water and blank control groups.We inject 50μl(5μg)IGF-I or 50μl sterile water to medial rectus muscles of experimental group or sterile water group respectively,then once every two weeks later.Collect binocula medial rectus muscles after 4,8 and 12 weeks.These samples were prepared for observation specimen of electron microscope.Perform statistical analysis of the internal rectus muscle myofibril irregular arrangement percentage,the abnormal rate of Z line and mitochondria number.Results(1)The myofibril irregular arrangement percentages in the experimenal groups are lower than the correspondingsterile water and blank control groups.The differences in 12 weeks are statistically significant(P<0.05).(2)The abnormal rate of Z line in theexperimenal groups are lower than the correspondingsterile water and blank control groups.The differences in 12 weeks are statistically significant(P<0.05).(3)The differences of mitochondria number in experimental,sterile water and blank control groups were not statistically significant(P>0.05).(4)There were positive relationship between myofibril irregular arrangement percentage and the abnormal rate of Z line and the development of strabismus in experimental group(r=0.886,0.957,P<0.01).There were positive relationship between myofibril irregular arrangement percentage and the abnormal rate of Z line and the development of strabismus in sterile water and blank control groups(rsterile water=0.956,0.985,P<0.01;rblank=0.939,0.988,P<0.01).The relationship of the mitochondria number and the development of strabismus were negative in all groups(r=-0.976,-0.982,-0.953,P<0.01).Conclusion(1)Exogenous IGF-I can make the degeneration of medial rectus muscles in cat model with exotropia slow down,so it may inhibit the process of muscle fiber atrophy.(2)The degenerative change of medial rectus muscls in cat model with exotropia increased with the prolongation of the course.