Meeting Abstract

P1.77  Saturday, Jan. 4 15:30  Effect of prenatal steroids on the citrate synthase activity of the guinea pig external abdominal oblique O’CONNELL, K.J.*; DEAROLF, J.L.; RICHMOND, J.P.; Hendrix College, Conway, AR; Univ. of North Florida, Jacksonville, FL oconnellkj@hendrix.edu

Glucocorticoids, a class of steroid hormones, are often used to stimulate lung development and combat mortality in the infants of women at risk of premature birth. Studies have shown improvement in the lung function of premature infants following gestational exposure to betamethasone, a glucocorticoid. However, the effects of glucocorticoids on the development of ventilatory muscles are not widely known. Studies in our laboratory demonstrated an increase in oxidative enzyme activity in fetal guinea pig scalenus muscles exposed to prenatal steroids compared to scalenus muscles not exposed to the steroid. Thus, we hypothesize that external abdominal oblique (EAO) muscles exposed to betamethasone during gestation will show greater oxidative enzyme activity than EAO muscles not exposed to the prenatal steroid. The activity of citrate synthase (CS), an enzyme involved in aerobic metabolism, will be measured by running enzyme kinetic assays on EAO muscles of guinea pig fetuses exposed to betamethasone or sterile water twice a week at 65%, 75%, and 85% gestation. The CS enzyme kinetic assay will be conducted on control and treated EAO muscles under the following conditions: 50 mM imidazole, 0.25 mM DTNB, 0.4 mM acetyl-CoA, and 0.5 mM oxaloacetate, pH 7.5 at 37°C. Data will be analyzed to determine if glucocorticoid exposure significantly increases CS activity in the EAO muscles of treated fetuses compared to those exposed only to sterile water. If the hypothesis is supported, babies exposed to prenatal steroids may have breathing muscles with significantly higher oxidative capacity and therefore, greater fatigue resistance than the muscles of babies not exposed to the steroid.