EFFECTS OF ZILPATEROL AND MELENGESTROL ACETATE ON BOVINE SKELETAL MUSCLE GROWTH AND DEVELOPMENT by ERIN KATHRYN SISSOM B.S., California State University, Fresno, 2002 M.S., Kansas State University, 2004 AN ABSTRACT OF A DISSERTATION submitted in partial fulfillment of the requirements for the degree DOCTOR OF PHILOSOPHY Department of Animal Sciences and Industry College of Agriculture KANSAS STATE UNIVERSITY Manhattan, Kansas 2009 Abstract Zilpaterol (ZIL) is a β-adrenergic receptor (β-AR) agonist that has been recently approved for use in feedlot cattle to improve production efficiencies and animal performance. One of the mechanisms through which this occurs is increased skeletal muscle growth. Therefore, two experiments were conducted to determine the effects of ZIL both in vivo and in vitro . In the first experiment, ZIL addition to bovine satellite cells resulted in a tendency to increase IGF-I mRNA and increased myosin heavy chain IIA (MHC) mRNA with 0.001 µ M and decreased MHC mRNA with 0.01 and 10 µ M. There were no effects of ZIL on protein synthesis or degradation. In myoblast cultures, there was a decrease in all three β-AR mRNA, and this was also reported in western blot analysis with a reduction in β2-AR expression due to ZIL treatment. In myotubes, there was an increase in β2-AR protein expression. In the second and third experiment, ZIL improved performance and carcass characteristics of feedlot steers and heifers. Additionally, ZIL decreased MHC IIA mRNA in semimembranosus muscle tissue collected from both steers and heifers. An additional part of the third study was conducted to determine the effects of melengestrol acetate (MGA) on bovine satellite cell and semimembranosus muscle gene expression. There were no effects of MGA on the expression of genes analyzed from semimembranosus muscle tissue collected. However, the addition of MGA to cultured bovine satellite cells resulted in increased β1 and β2-AR mRNA. These experiments aid in our understanding of the mechanism of action of MGA in heifers, as well as the effects of ZIL on both steers and heifers. Furthermore, they increase our knowledge and understanding of the mechanism of action of ZIL, as well as other β-agonists used to promote growth and efficiency in feedlot animals. EFFECTS OF ZILPATEROL AND MELENGESTROL ACETATE ON BOVINE SKELETAL MUSCLE GROWTH AND DEVELOPMENT by ERIN KATHRYN SISSOM B.S., California State University, Fresno, 2002 M.S., Kansas State University, 2004 A DISSERTATION submitted in partial fulfillment of the requirements for the degree DOCTOR OF PHILOSOPHY Department of Animal Sciences and Industry College of Agriculture KANSAS STATE UNIVERSITY Manhattan, Kansas 2009 Approved by: Major Professor Dr. Bradley J. Johnson Abstract Zilpaterol (ZIL) is a β-adrenergic receptor (β-AR) agonist that has been recently approved for use in feedlot cattle to improve production efficiencies and animal performance. One of the mechanisms through which this occurs is increased skeletal muscle growth. Therefore, two experiments were conducted to determine the effects of ZIL both in vivo and in vitro . In the first experiment, ZIL addition to bovine satellite cells resulted in a tendency to increase IGF-I mRNA and increased myosin heavy chain IIA (MHC) mRNA with 0.001 µ M and decreased MHC mRNA with 0.01 and 10 µ M. There were no effects of ZIL on protein synthesis or degradation. In myoblast cultures, there was a decrease in all three β-AR mRNA, and this was also reported in western blot analysis with a reduction in β2-AR expression due to ZIL treatment. In myotubes, there was an increase in β2-AR protein expression. In the second and third experiment, ZIL improved performance and carcass characteristics of feedlot steers and heifers. Additionally, ZIL decreased MHC IIA mRNA in semimembranosus muscle tissue collected from both steers and heifers. An additional part of the third study was conducted to determine the effects of melengestrol acetate (MGA) on bovine satellite cell and semimembranosus muscle gene expression. There were no effects of MGA on the expression of genes analyzed from semimembranosus muscle tissue collected. However, the addition of MGA to cultured bovine satellite cells resulted in increased β1 and β2-AR mRNA. These experiments aid in our understanding of the mechanism of action of MGA in heifers, as well as the effects of ZIL on both steers and heifers. Furthermore, they increase our knowledge and understanding of the mechanism of action of ZIL, as well as other β-agonists used to promote growth and efficiency in feedlot animals. Table of Contents List of Figures................................................................................................................................vii List of Tables...................................................................................................................................x Acknowledgments..........................................................................................................................xi Dedication......................................................................................................................................xii CHAPTER 1 – Review of Literature.............................................................................................. 1 Introduction...................................................................................................................................2 Metabolic Modifiers......................................................................................................................2 β-adrenergic Receptors.................................................................................................................5 Postnatal Skeletal Muscle Growth and the Muscle Satellite Cell.................................................7 β-adrenergic Receptor Agonists..................................................................................................10 β-adrenergic Receptor Agonists and Muscle Growth.................................................................11 β-adrenergic Receptor Agonist Use in Livestock Species..........................................................16 Literature Cited...........................................................................................................................20 CHAPTER 2 - Effects of Zilpaterol on Cultured Bovine Satellite Cells.......................................29 Abstract...................................................................................................................................... 30 Introduction.................................................................................................................................32 Materials and Methods................................................................................................................33 Results and Discussion...............................................................................................................40 Literature Cited...........................................................................................................................50 CHAPTER 3 - Effect of Zilpaterol on Feedlot Steer Performance, Carcass Characterstics and Skeletal Muscle Gene Expression..................................................................................................79 v Abstract.................................................................................................................................... ..80 Introduction.................................................................................................................................82 Materials and Methods................................................................................................................83 Results and Discussion...............................................................................................................85 Literature Cited...........................................................................................................................91 CHAPTER 4 - Effect of Zilpaterol and Melengestrol Acetate on Skeletal Muscle Gene Expression in Feedlot Heifers and Cultured Bovine Satellite Cells............................................104 Abstract……………………………………………………………………………………….105 Introduction...............................................................................................................................107 Materials and Methods..............................................................................................................108 Results and Discussion.............................................................................................................111 Literature Cited.........................................................................................................................119 Dissertation Summary...............................................................................................................142 vi List of Figures Figure 2.1 Effect of zilpaterol on [ 3H]-thymidine incorporation in bovine satellite cells (BSC)..56 Figure 2.2 Effect of zilpaterol on BSC proliferating myoblast β1-AR mRNA.............................57 Figure 2.3 Effect of zilpaterol on BSC proliferating myoblast β2-AR mRNA.............................58 Figure 2.4 Effect of zilpaterol on BSC proliferating myoblast β3-AR mRNA.............................59 Figure 2.5 Effect of zilpaterol on BSC proliferating myoblast IGF-I mRNA...............................60 Figure 2.6 Effect