Meeting Abstract

93.5  Sunday, Jan. 6  Estrogen Dose Influences Medullary Bone Quantity and Density in Female Pine Siskins SQUIRE, M.E. *; VEGLIA, M.K.; DRUCKER, K.A.; HAHN, T.P; WATTS, H.E.; The University of Scranton; The University of Scranton; The University of Scranton; The University of California, Davis; Loyola Marymount University maria.squire@scranton.edu

Medullary bone is a non-structural type of bone tissue that can serve as labile calcium reservoir for the production of calcified eggshells. Previous research has shown that medullary bone formation precedes eggshell formation and is influenced, in part, by rising estrogen levels. In the current study, we examined the effect of estrogen (E2) treatment on medullary bone quantity and mineralization in female Pine Siskins (Carduelis pinus). Over a five-month period, females received one of three treatments: high dose E2 (n=4), low dose E2 (n=3), or no E2 (n=8). After sacrifice, high resolution (10 μm) micro-computed tomography scanning (Scanco Medical, SUI) was done on the femora and humeri to determine average medullary bone quantity (BV/TV) and its density (mg HA/ccm) across the two bones for each bird. In the 15 females examined, medullary BV/TV ranged from scant (3%) to abundant (83%) and minimally (490.0 mg Ha/ccm) to highly (1184.6 mm Hg/ccm) mineralized. We found that the E2 dose had a significant effect on the average medullary BV/TV and average density for each bird (p<0.05), with the high estrogen treatment group having the greatest average medullary BV/TV (78.6%) and the highest average density (1161.9 mg HA/ccm). We are currently investigating the relationship between bone measures and ovarian development and future studies are needed to examine the timeline of medullary bone formation and resorption in greater detail.