Meeting Abstract
Prenatal steroids are known to accelerate the development of the lungs of premature human babies; however, to date it is unknown whether they have a similar effect on ventilatory muscles. To determine if exposure to a multi-course treatment of betamethasone, a commonly used prenatal steroid, accelerates breathing muscle development in guinea pigs (Cavia porcellus), the percentages and sizes of types IIA and IIX fast-twitch fibers of the neonatal guinea pig rectus abdominis (RA), an accessory ventilatory muscle, were determined. In addition, the citrate synthase (CS) activity and myoglobin concentration in this muscle were quantified. These features were compared to those of fetal guinea pig muscles that were exposed to multi-course betamethasone to see if the characteristics of the treated fetal muscles match those of the neonatal muscles. Immunocytochemistry using an antibody to type IIA myosin (2F7) was used to identify and determine the percentages of the fast IIA and IIX fiber-types in one-day-old neonatal RA muscles. In addition, CS activity in these muscles was measured using kinetic assays. Finally, SDS-PAGE was performed to separate and measure the myoglobin concentration relative to actin in the neonatal muscle samples. If the characteristics of the neonatal and prenatal steroid-treated RA muscles are similar, these results would support the hypothesis that prenatal steroids accelerate breathing muscle development. This result would be incredibly important for babies and mothers exposed to prenatal steroids. Increased understanding about the effects of these steroids will help mothers at risk for premature birth of their infants make more informed decisions during their pregnancies and keep their babies safe.
