Meeting Abstract

P2.80  Tuesday, Jan. 5  The effects of betamethasone on myosin expression patterns of fetal Cavia porcellus rectus thoracis muscle SCHROEDER, J.R.**; MCCORMICK, M.M.; PREHODA-WYERS, M.M.; DEAROLF, J.L.; Hendrix College, Conway, AR schroederjr@hendrix.edu

Betamethasone, a glucocorticoid, can be administered to pregnant women likely to give birth prematurely in order to accelerate the development of their fetus’ organs. While much research has focused on determining the effects of this treatment on fetal lungs, little research has been conducted on their effects on the ventilatory muscles. Glucocorticoids are known to switch the cell cycle from proliferation to differentiation. In muscles, differentiation involves changes in myosin heavy chain expression. Specifically, fetal myosin will decrease in expression and is replaced by adult isoforms: neonatal, IIA, IIX (fast) and I (slow). From these ideas, our hypothesis is that the Cavia porcellus fetal rectus thoracis exposed to glucocorticoids will display more adult fast (neonatal, IIA, IIX) myosin isoforms than control muscles. To test this hypothesis, pregnant guinea pigs were injected with either betamethasone (0.5 mg/kg) (treated) or with sterile water (control) at 70% gestation. An assessment of the fetal myosin profile occurred with the use of 7% acrylamide, 30% glycerol gels ran at 275V, 10° C for 24 hours. After silver staining and drying, the gels were analyzed with Scion Image in order to determine the proportions of fetal, neonatal/IIA/IIX, and slow MHC isoforms each sample expressed. If our hypothesis is supported, the treated fetal rectus thoracis will contain more adult fast myosins than our control muscles. Therefore, the treated muscle should then express the characteristics, fatigue resistance, and oxidative capabilities of adult muscle. These abilities potentially mean that the rectus thoracis muscle will have more functionality in the case of pre-mature birth and be better suited to support neonatal ventilatory demands.