Meeting Abstract

P1.76  Saturday, Jan. 4 15:30  Effect of prenatal steroids on the myoglobin concentration in the diaphragm of fetal guinea pigs LAVERGNE, J.N.**; DEAROLF, J.L.; Hendrix College, Conway, AR lavergnejn@hendrix.edu

Currently, glucocorticoids are used to promote the survival of premature children by accelerating their lung development. However, very little is known presently about how these steroids affect breathing muscle development. Work in our laboratory has shown that one of these steroids, betamethasone, increases the concentration of NADH-D, an oxidative enzyme, in an accessory inspiratory muscle of guinea pigs. These results suggest prenatal glucocorticoids accelerate the acquisition of mitochondria by fetal muscle, and to support the generation of ATP by these organelles, the fetal muscle would therefore require more oxygen. Thus, we propose that glucocorticoids will increase the concentration of myoglobin (Mb), the oxygen carrier in muscles, in the diaphragm (DIA) of fetal guinea pigs. To test this hypothesis, pregnant guinea pigs were given three injections of betamethasone (0.5 mg/kg) at 65%, 75% and 85% gestation. Twenty-four hours after the last injection, the females and their fetuses were euthanized and fetal tissue was collected. Extracts of the fetal muscle samples were prepared and separated in SDS-polyacrylamide (12%) gels for ~ 2 hours (30 mA/gel) at 16° C. These gels were silver stained, and ImageJ software was used to determine the proportion of Mb relative to actin in the treated and control DIA muscles. If Mb concentrations are higher in the treated muscles, they may be better able to deliver oxygen to their mitochondria and thereby resist fatigue in comparison to non-treated muscles. Thus, babies exposed to prenatal steroids will have more mature DIA muscles and be better prepared to respond to ventilatory challenges.