Meeting Abstract

P3.43  Thursday, Jan. 6  Effect of glucocorticoids on glycogen storage in fetal Cavia porcellus breathing muscles STEWART, A.C.*; PREHODA-WEYERS, M.M.; DEAROLF, J.L.; Hendrix College, Conway, AR stewartac@hendrix.edu

In prenatal care, glucocorticoids are injected into mothers expecting premature birth. The synthetic steroids speed up development of the lungs, including accelerating the production of lung surfactant, which increases the odds of a premature baby’s survival. However, researchers have found that these steroids lead to a reduction in glycogen storage in the quadriceps of treated rats, and they hypothesized that this reduction could be due to increased muscular activity in the glucocortcoid-exposed rats. Thus, we hypothesized that fetal guinea pigs treated with the glucocorticoid, betamethasone, would store less glycogen in the fibers of their breathing muscles than untreated fetal guinea pigs. To test this hypothesis, pregnant guinea pigs were injected with betamethasone (0.5 mg/kg of body weight), or sterile water at 65%, 75%, and 85% gestation. At 59 days gestation, the pregnant guinea pigs were sacrificed, and breathing muscle (diaphragm and rectus abdominis) samples were collected from their fetuses. Serial sections of these samples were stained for their glycogen content using the Periodic Acid Schiff reaction and for their myosin ATPase activity. Scion image was used to measure the staining densities of the slow-and fast-twitch fibers and thus, quantify their glycogen content. The percent light-and dark-staining slow-and fast-twitch fibers were calculated using z-scores. If the hypothesis were supported, betamethasone exposed fetuses may have problems sustaining their breathing, because of the decreased amount of fuel, glycogen, in the fibers of their breathing muscles.