Meeting Abstract

P3.27  Tuesday, Jan. 6  Can the maternal weight of a guinea pig be used to determine the glucocorticoid steroid dose to its fetuses? TAYLOR, K.N.**; WEIGAND, K.L.; BAATZ, J.E.; DEAROLF, J.L.; Hendrix College, Conway, AR; the Medical University of South Carolina, Charleston taylorkn@hendrix.edu

Glucocorticoid steroids accelerate the development of body organs before birth and are therefore given to mothers who are expected to give birth prematurely, primarily to stimulate the development of their fetuses lungs. However, from previous studies, we hypothesize that prenatal glucocorticoids will decrease the percentage of fast twitch fibers in the breathing muscles of guinea pigs, which would affect the ability of these muscles to contract quickly during ventilatory challenges. To test this hypothesis, a steroid dosage protocol based on a study in fetal sheep was used, in which the mothers weight determined the amount of steroid administered (0.5mg steroid/kg maternal weight at 65%, 75% and 85% gestation). But, given that maternal weight is not a good indicator of litter size in guinea pigs, it is not known if all of the fetuses in this study have received the appropriate steroid dose. Since glucocorticoids stimulate lung surfactant production, the presence of these proteins can be used to determine if the fetuses have received this dosage. Lung samples were collected from all fetuses in the study and prepared for SDS-polyacrylamide gel electrophoresis. Proteins were separated using nonreducing conditions on a 12% Tris/Glycine SDS-PAGE gel, run at 200V for 40 minutes and transferred (25V, 80 min) to nitrocellulose membranes for Western Blots. Membranes were probed with an anti-lung surfactant protein B (SP-B) primary antibody and developed using chemiluminescence. Relative changes in SP-B as a function of glucocorticoid exposure were then used to determine the validity of using the mothers weight as a basis for the dosage of these steroids in animals that give birth to litters.