Meeting Abstract

P1.165  Wednesday, Jan. 4  Do multiple doses of betamethasone increase the oxidative capacity of the fetal guinea pig scalenus muscle? WALKER, R.A.**; DORNHOFFER, T.M.; DEAROLF, J.L.; Hendrix College, Conway, AR walkerra@hendrix.edu

One dose of prenatal steroids has been shown to aide in the respiratory development of premature babies, without any significant detrimental side effects to either the infant or the mother. However, it is unclear whether multiple doses of prenatal steroids have a more profound positive effect, or whether they are accompanied by harsh side effects. Previous research in our lab indicated that a multi-course exposure to betamethasone actually increased the oxidative capacity of the fetal guinea pig scalenus, an accessory inspiratory muscle. However, additional research and a more standardized method of data collection are necessary to support our hypothesis that multiple doses of prenatal betamethasone actually increase the oxidative capacity of this muscle. Scalenus samples were collected from fetal guinea pigs that were exposed to multiple doses of betamethasone, or sterile water, (2 injections per week, 24-hours apart at 65%, 75%, and 85% gestation) prior to collection of muscle samples. Each sample was cut in a cryostat, and the sections were stained for their NADH-tetrazolium reductase (NADH-TR) or myosin ATPase activity. The density of NADH-TR staining was measured in the slow and fast twitch fibers in each fetal muscle using Scion Image. Z-scores were then calculated and used to identify the proportions of slow and fast twitch fibers staining darkly and lightly for NADH-TR. If our hypothesis is supported, the NADH-TR activity of both slow and fast twitch scalenus muscle fibers will increase with multiple doses of betamethasone. Thus, the breathing muscles of steroid treated fetuses will have an increased oxidative capacity compared to the muscles of non-treated fetuses, which is indicative of a higher fatigue resistance and overall stronger ventilatory capacity.