Meeting Abstract

28.1  Wednesday, Jan. 5  Effects of glucocorticoid administration on the contractile properties of the fetal guinea pig diaphragm SCIORTINO, A.**; PREHODA-WYERS, M.M.; DEAROLF, J.L.; Hendrix College, Conway, AR sciortinoaa@hendrix.edu

Glucocorticoids have been administrated to pregnant mothers at risk of preterm delivery in order to stimulate fetal lung development. The application of these steroids improves neonatal viability, such that the fetus will be able to live and function independently from the mother. However, the impact of glucocorticoids on the development of breathing muscles is not well known. Glucocorticoids have been shown to affect the development of fetal sheep hindlimb muscles by leading to a loss of fast twitch fibers. Further experimentation has shown that exposure to these same glucocorticoids results in smaller fibers in adult breathing muscles, such as the diaphragm. Thus, these results suggest that the administration of glucocorticoids leads to smaller muscles, which in turn, may lead to a decrease in force production. Therefore, we hypothesize that glucocorticoid treatment during muscle fiber differentiation will decrease the overall force production of the diaphragm in the guinea pig. To test these hypotheses, we will remove diaphragm muscles from fetal guinea pigs that have been exposed to multiple courses of betamethasone (at 65%, 75%, and 85% gestation) or sterile water (control). We will measure and compare the contraction abilities of these muscles, specifically the maximum twitch force (normalized to muscle cross-sectional area). If the hypothesis is supported, our results would indicate that a multi-course exposure to betamethasone could be a detriment to the development of diaphragm in fetal guinea pigs. Therefore, babies exposed to prenatal glucocorticoids may have a higher risk of having respiratory complications due to an immature and underdeveloped diaphragm.