Meeting Abstract

P1.168  Wednesday, Jan. 4  Determining the effect of prenatal steroids on the rectus abdominis of Cavia porcellus REDO, A.R.**; WALKER, R.A.; DEAROLF, J.L.; Hendrix College, Conway, AR redoar@hendrix.edu

Glucocorticoid steroids are widely used as a precaution for women who risk premature labor. These steroids accelerate lung development in babies born premature, but may come with side effects like weight loss and lung problems later in life. The focus of this research project is to determine the effects of prenatal steroid treatment on the glycogen storage in the fast- and slow-twitch fibers of the guinea pig rectus abdominis muscle. Based on work completed in our lab, which showed a higher oxidative capacity in a breathing muscle exposed to prenatal steroids, we hypothesize that more glycogen, the fuel of muscle contraction, is stored in the fibers of fetuses that are exposed to the steroids. To test this hypothesis, pregnant Hartley guinea pigs were injected with betamethasone or sterile water at 65%, 75%, and 85% gestation. Twenty-four hours after the last injection, each female guinea pig was humanely euthanized and her fetuses extracted. The rectus abdominis muscle was removed from each fetus and prepared for histochemistry. Once the tissue was cut in a cryostat and mounted onto slides, it was stained for myosin ATPase activity and glycogen content using the Periodic Acid Schiff reaction. Digital images of the stained tissue were taken, the fast- and slow-twitch fibers were identified, and their glycogen staining densities measured using Scion Image. Z-scores will be calculated and used to determine the percentages of fast- and slow-twitch fibers staining darkly or lightly for glycogen. If we find a greater storage of glycogen in treated breathing muscles, the breathing muscles of babies exposed to these steroids may be capable of contracting for extended periods of time, because of the larger fuel reserves in their fibers.