Meeting Abstract

P2.83  Tuesday, Jan. 5  Effects of betamethasone on the extensor digitorum longus in fetal guinea pigs LIMONCELLI, K.A.**; PREHODA-WYERS, M.M.; DEAROLF, J.L.; Hendrix College, Conway, AR limoncellika@hendrix.edu

Studies indicate that in skeletal muscle tissue, the process of differentiation includes the disappearance of fetal and neonatal myosin heavy chain (MHC) expression and replacement of these developmental myosins by adult MHC IIA, IIX, and IIB. It is also known that glucocorticoids are responsible for activating differentiation in tissues, and synthetic glucocorticoid administration is a common protocol used to increase the survival rate of premature newborns. This study is designed to determine the effects of synthetic glucocorticoids on myosin expression and myogenesis in fetal guinea pig muscle tissue, specifically the extensor digitorum longus (EDL). Two injections of betamethasone or sterile water were administered to pregnant females (0.5 mg/kg) at 70% gestation (day 47 and 48). EDL muscle samples were collected from treated and control fetuses, frozen, and prepared for 7% polyacrylamide, 30% glycerol SDS gels. Three bands (fetal, neonatal/IIA/ IIX, and slow) were identified and the proportion of each myosin present relative to the total myosin expressed by the fetal EDLs was determined using SCION image. If our results support the hypothesis, more adult fast myosin will be present in the treated muscles, indicating that the transition from fetal and neonatal myosin to the adult myosins occurs faster in treated fetuses. These findings may indicate an alteration of contractibility and fatigability in treated muscles. Studies show, as adult fast myosin increases, the contractile force and fatigability increase, suggesting that treated muscles will have better contractile properties than control. However, high fatigue resistance might be a necessary trait in postnatal development into adulthood, suggesting a possible negative outcome from exposure to the drug.