East Tennessee State University Digital Commons @ East Tennessee State University Electronic Theses and Dissertations Student Works 12-2004 Dose-Dependent Effects of Salmon Calcitonin on Bone Turnover in Ovariectomized Rats. Beatrice H. Owens East Tennessee State University Follow this and additional works at: https://dc.etsu.edu/etd Part of the Medical Sciences Commons Recommended Citation Owens, Beatrice H., "Dose-Dependent Effects of Salmon Calcitonin on Bone Turnover in Ovariectomized Rats." (2004). Electronic Theses and Dissertations. Paper 977. https://dc.etsu.edu/etd/977 This Dissertation - Open Access is brought to you for free and open access by the Student Works at Digital Commons @ East Tennessee State University. It has been accepted for inclusion in Electronic Theses and Dissertations by an authorized administrator of Digital Commons @ East Tennessee State University. For more information, please contact [email protected]. Dose-dependent Effects of Salmon Calcitonin on Bone Turnover in Ovariectomized Rats _______________ A dissertation presented to the faculty of the Department of Anatomy and Cell Biology East Tennessee State University _______________ In partial fulfillment of the requirements for the degree Doctor of Philosophy in Biomedical Science _______________ by Beatrice H. Owens December 2004 ________________ Dr. Ronald C. Hamdy, Co-Chair Dr. Fred E. Hossler, Co-Chair Dr. Kenneth Ferslew Dr. Ellen Rasch Dr. Richard Skalko Keywords: bone formation, bone mineral density, bone resorption, bone turnover, calcitonin, osteoblasts, osteoclasts, osteoporosis, ovariectomy, remodeling Dose-dependent Effects of Salmon Calcitonin on Bone Turnover in Ovariectomized Rats by Beatrice H. Owens In the United States, osteoporosis results in about 1.5 million annual fractures, costing approximately $15 billion. Calcitonin is safe and effective in slowing osteoporotic bone loss, but its effect is transient. The current studies were designed to explore the dose- dependent effects of salmon calcitonin on bone turnover in ovariectomized rats and to determine if the decrease in therapeutic effectiveness of calcitonin demonstrated over time with higher doses is due to oversuppression of bone turnover. Doses of 5, 15, & 50 IU/kg BW/day of calcitonin were compared to placebo in 12-week-old ovariectomized and sham-ovariectomized Sprague-Dawley rats for 24 weeks. The spinal bone mineral content (BMC) as measured by DXA in ovariectomized subjects receiving 5 & 15 IU/kg of calcitonin was not significantly different from sham-ovariectomized subjects, while spinal BMC of subjects receiving 50 IU/kg was significantly lower than sham- ovariectomized subjects (p<0.05). Femoral BMC of ovariectomized subjects was significantly lower than sham-ovariectomized subjects (p<0.05), but no significant differences were noted between treatment groups. Scanning electron microscopy (SEM) demonstrated a decrease in number and density of trabeculae and in cortical thickness when comparing femurs from ovariectomized with sham-ovariectomized subjects. SEM of subjects receiving 50 IU/kg displayed greater bone loss than other groups. No significant differences were noted between groups for levels of urinary helical peptides or serum pyridinoline [ELISA], indicators of bone resorption. Urinary calcium excretion [capillary ion electrophoresis] was significantly higher in subjects receiving 50 IU/kg of 2 calcitonin than other ovariectomized subjects (p<0.05). Serum levels of osteocalcin [RIA], an indicator of bone formation, were significantly higher in subjects receiving 5 IU/kg of calcitonin than control subjects and those receiving 50 IU/kg (p<0.05). Production of antibodies to calcitonin [ELISA] by subjects in this study did not correlate with changes in bone turnover or bone density. The results of this study do not provide evidence higher doses of calcitonin result in oversuppression of bone turnover. However, urinary calcium excretion affected bone resorption in a reverse dose-dependent manner, suggesting the calciuric effect may be responsible for less effective outcomes seen with higher doses of calcitonin. 3 ACKNOWLEDGEMENT I would first like to thank the chairmen of my Ph.D. committee, Dr. Ronald C. Hamdy and Dr. Fred E. Hossler. Dr. Hamdy has provided professional guidance, persistent encouragement, and extensive resources to allow for completion of this dissertation research project. I am grateful to his staff, including Judy Beamer-Morey, Ashley Blevins, Heather Campbell, Denelle Hensley, and Gerard Daly, for their assistance with surgical procedures, densitometry scans, and dissections. I am forever indebted to Dr. Hossler for his advice, encouragement, and support during my Ph.D. studies and for his assistance with SEM images for my dissertation project. I am grateful to the remainder of my Ph.D. committee members for their assistance and support as well. Dr. Ferslew has provided consistent encouragement and assistance with statistical analyses of data, training, and completion of experiments and has offered invaluable advice for completion of my dissertation project. I would also like to commend and thank Dr. Rasch and Dr. Skalko for their contributions, suggestions, and continued support. I would like to express my sincere gratitude to the faculty and staff in the Cardiovascular Research Lab. Dr. Chu C. Chua and Mrs. Cathy Landy were invaluable with their advice, technical instruction, training, and assistance for completion of experiments. Dr. Zhongyi Chen and Dr. Xuwan Liu assisted with initial training for surgical procedures for this dissertation project. Dr. Balvin H.L. Chua has provided 4 support and advice, as well as allowing for use of his lab equipment, and Xingshun Xu assisted with computer graphics and techniques. I would like to express my appreciation to Dr. Mitch Robinson and Beverly Sherwood for their continued support, advice, and encouragement. I am grateful to the staff of the Department of Laboratory Animal Resources for their technical advice, training, support, and encouragement. I am thankful to Dr. George Youngberg for analyzing our ovarian tissue samples. I am also appreciative of Dr. Carole Williams in the Department of Physiology for use of her equipment and assistance with Radioimmunoassay measurements. Finally, I would like to thank my family for their unending love, support, prayers, and encouragement during my Ph.D. experience. 5 CONTENTS Page ABSTRACT .......................................................................................................................... 2 ACKNOWLEDGEMENT ..................................................................................................... 4 LIST OF TABLES ................................................................................................................ 12 LIST OF FIGURES .............................................................................................................. 13 Chapter 1. INTRODUCTION ........................................................................................................ 15 Description of Bone................................................................................................... 16 Osteoclasts ........................................................................................................... 19 Osteoblasts ........................................................................................................... 20 Osteocytes............................................................................................................ 21 Functions of Bone................................................................................................ 21 Bone Physiology........................................................................................................ 22 Regulation of Bone Remodeling................................................................................ 23 Role of Systemic Hormones in Regulation of Bone Remodeling ............................. 24 Role of Local Factors in Regulation of Bone Remodeling........................................ 29 Chronological Changes in Bone ................................................................................ 31 Disorders of Bone Remodeling.................................................................................. 34 Osteoporosis............................................................................................................... 36 Description of Osteoporosis................................................................................. 36 6 Factors Affecting Osteoporosis............................................................................ 38 Non-modifiable Factors Affecting Osteoporosis........................................... 39 Modifiable Factors Affecting Osteoporosis................................................... 39 Histological Analysis of Bone Turnover ................................................................... 40 Analysis of Bone Quality........................................................................................... 41 Measurement of Urinary Calcium Excretion............................................................. 45 Measurement of Bone Turnover ................................................................................ 47 Biochemical Analyses of Bone Resorption ......................................................... 47 Biochemical Analyses of Bone Formation .......................................................... 48 Limitations of Biochemical