Meeting Abstract

P1.164  Wednesday, Jan. 4  Betamethasone treatment of the diaphragm of fetal Cavia porcellus: a look at glycogen storage LEE, R.J.**; WALKER, R.A.; DEAROLF, J.L.; Hendrix College, Conway, AR

Prenatal steroid use has shown benefits in accelerating fetal lung development in women at risk of preterm birth. However, the effects of these steroids on breathing muscle development are not as well known. Previous work in our lab demonstrated that steroid treatment leads to higher oxidative enzyme concentrations in treated muscles. Therefore, we hypothesize that there will be more glycogen stored in the fibers of treated muscles to support the fuel requirements of the oxidative enzymes. To study the effects of prenatal steroids on the glycogen storage of fetal diaphragms, pregnant guinea pigs were injected with betamethasone or sterile water twice a week, 24-hours apart, for three weeks at 65%, 75%, and 85% gestation. At 59 days of gestation, the guinea pig mothers were sacrificed, and fetal diaphragm tissue samples were taken. These samples were cut in a cryostat, and sections of these samples underwent myosin ATPase and glycogen staining. The stained sections were imaged, and the glycogen staining density was measured using Scion Image. Staining densities were converted into Z-scores, which were then used to calculate the percentages of slow- and fast-twitch fibers staining lightly or darkly for glycogen. If our hypothesis is supported, prenatal steroid treatment will lead to diaphragms with a high level of glycogen storage, which will make these muscles more fatigue resistant in comparison to the diaphragms in untreated preemies. Knowing the effects of these steroids on the development of the diaphragm could allow physicians and expecting mothers to make more informative decisions about prenatal steroid use.