The Change Of Muscle Fibro Type And Glycogen Content In Diaphragmatic Muscle On Acquired Pectus Excavatum In Rats

Objective:By the study of the percentage of different types on diaphragmatic muscle fibre and the change of the glycogen content on acquired pectus excavatum in rats, we want to investigate the influence of the deformity of pectus excavatum on the diaphragmatic muscle function, so to provide theoretical basis with the further mechanism study of the damaged lung function, which is caused by pectus excavatum.Method:We randomly divided 40 four-week Sprague Dawley(SD)rats, which were from the same batch but different brood into experimental group and control group. Each group had 20 rats. The 20 rats in experimental group were used to make the model of pectus excavatum through parasternally disconnecting the lower three pairs of costal cartilage. However,20 in control group were used as blank without any inteference. Twelve weeks after the operation, we executed 10 rats from the control group and 10 with obvious deformity of anterior chest wall from experimental group, taking the costal and diaphragmatic muscle stripes. Coloretured by enzyme histochemistry dripping-straining method, we can identify type I and type II muscle fibre. Then we counted them with optical microscope, analyzing the percentage of different types of muscle fibre. We used anthracene copper coloration method to measure the the glycogen content. The t-test was used to do the statistical analysis of the results. There was statistically significant difference when p<0.05.Results:All of the rats of experimental group after operation presented deformity of pectus excavatum.①The percentage of type I muscle fiber in each group was 45.7 %±5.8%,37.8%±6.1% separately. While the percentage of typeⅡmuscle fibre in each group was 54.3%±5.8%,62.2%±6.1% separately. The percentage of type I muscle fiber in experimental group was higher than the one in the control group(p<0.05), however, the percentage of typeⅡmuscle fiber was lower(p<0.05).②The glycogen content in 100g diaphragmatic muscle fiber in experimental group was 0.091±0.008g, whereas it was 0.060±0.011g in control group. It showed that the glycogen content in experimental group was significantly higher than the control group (p<0.01).Conclusion:The reserved glycogen content of the diaphragmatic muscle on acquired pectus excavatum in rats increased. And the oxidizing ability of rib diaphragmatic muscle also enhanced. However, with the increased percentage of slow oxidative fiber, the contractile function decreased. And the expansion of the lower rib cage was limited when inhaling.