Meeting Abstract

P1.124  Sunday, Jan. 4  Effects of betamethasone on the fetal rectus abdominus of the guinea pig (Cavia porcellus) CUPP, C.S.**; THOMPSON, K.E.; WEIGAND, K.L.; DEAROLF, J.L.; Hendrix College, Conway, AR cuppcs@hendrix.edu

Betamethasone is a corticosteroid often used to stimulate the development of the lungs and initiate the production of pulmonary surfactant proteins of infants. The intent of this project was to examine the effects of betamethasone on the fetal rectus abdominus, an expiratory muscle of Cavia porcellus. Corticosteroids accelerate tissue and organ development by stimulating cells to stop dividing and start differentiating. Therefore, we hypothesize that the expression of adult myosin heavy chain isoforms (fast: IIA, IIX; slow: I) will be higher in the muscles of treated fetuses. Pregnant guinea pigs were injected twice (0.5 mg/kg maternal weight), twenty-four hours apart at 70% gestation with either betamethasone (treated) or sterile water (control). Rectus abdominus samples were collected from each treated and control fetus and prepared for SDS-polyacrylamide gel electrophoresis. Aliquots of diluted myosin were electrophoresed for 24 hours at 275V and 8C in a 7% acrylamide, 30% v/v glycerol separating gel. Gels were silver stained, dried, and scanned into a computer. Scion Image was used to quantify the proportions of the adult myosin heavy chain isoforms present within the total myosin of each sample. If increased expression of adult myosin isoforms occurs in the treated rectus abdominus, these muscles may have contractile properties more similar to adult muscles than fetal rectus abdominus muscles not exposed to prenatal steroids. Thus, when the steroid-exposed fetuses are born, their breathing muscles will be better able to deal with ventilatory challenges, such as infection, than the muscles of unexposed neonates.