CONTROL OF LUTEOLYSIS IN THE MARE Vanda Gonçalves dos Santos Tese apresentada à Universidade de Évora para obtenção do Grau de Doutor em Ciências Veterinárias ORIENTADORA: Elisa Maria Varela Bettencourt ÉVORA, MAIO 2015 INSTITUTO DE INVESTIGAÇÃO E FORMAÇÃO AVANÇADA CONTROL OF LUTEOLYSIS IN THE MARE Vanda Gonçalves dos Santos Tese apresentada à Universidade de Évora para obtenção do Grau de Doutor em Ciências Veterinárias ORIENTADORA: Elisa Maria Varela Bettencourt ÉVORA, MAIO 2015 INSTITUTO DE INVESTIGAÇÃO E FORMAÇÃO AVANÇADA i TABLE OF CONTENTS Abstract .....................................................................................................................................v Resumo .................................................................................................................................... vi Acknowledgments .................................................................................................................. ix List of figures .......................................................................................................................... xi List of tables.......................................................................................................................... xvi List of abbreviations ........................................................................................................... xvii Preamble .................................................................................................................................19 1. Literature review ...............................................................................................................20 1.1. Introduction .....................................................................................................................20 1.2.1. Follicular phase ............................................................................................................20 a) The wave phenomenon ........................................................................................................20 b) Emergence ...........................................................................................................................21 c) Acquisition of dominance / Deviation .................................................................................22 d) Follicular growth, periovulatory period and ovulation ........................................................27 1.2.2. Luteal phase ..................................................................................................................30 a) Corpus luteum ......................................................................................................................30 b) Corpus hemorragicum .........................................................................................................31 c) Luteolysis .............................................................................................................................31 1.2.3. Abnormalities of the estrous cycle ..............................................................................34 a) Hemorrhagic anovulatory follicles ......................................................................................34 b) Idiopathic persistence of the corpus luteum ........................................................................35 2. Oxytocin induction of pulses of a prostaglandin metabolite and luteolysis in mares. .38 Abstract ...................................................................................................................................39 2.1. Introduction .....................................................................................................................40 2.2. Materials and methods ...................................................................................................42 ii 2.2.1. Mares and treatments .....................................................................................................42 2.2.2. Experiment 1. Effect of bolus treatment with OT on PGFM .........................................43 2.2.3. Experiment 2. Effect of 2-h infusion of OT on PGFM pulses .......................................43 2.2.4. Experiment 3. Effect of FM bolus treatment and OT infusion on P4. ...........................44 2.2.5. Experiment 4. Effect of FM bolus treatment and OT infusion on PGFM and P4. ........45 2.2.6. Hormone assays .............................................................................................................45 2.2.7. Statistical analyses .........................................................................................................46 2.3. Results ..............................................................................................................................47 2.3.1. Experiment 1. Effect of bolus treatment with OT on PGFM .........................................47 2.3.2. Experiment 2. Effect of 2-h infusion of OT on PGFM pulses .......................................48 2.3.3. Experiment 3. Effect of FM bolus treatment and OT infusion on P4 ............................51 2.3.4. Experiment 4. Effect of FM bolus treatment and OT infusion on PGFM and P4 .........52 2.4. Discussion.........................................................................................................................54 2.5. Conclusions ......................................................................................................................57 2.6. Acknowledgments ...........................................................................................................58 2.7. References ........................................................................................................................58 3. Role of PGF2α in luteolysis based on inhibition of PGF2α synthesis in the mare. ......64 Abstract ...................................................................................................................................65 3.2. Materials and methods ...................................................................................................68 3.2.1. Mares..............................................................................................................................68 3.2.2. Protocol ..........................................................................................................................69 3.2.3. Hormone assays .............................................................................................................71 3.2.4. Statistical analyses .........................................................................................................71 3.3. Results ..............................................................................................................................72 3.4. Discussion.........................................................................................................................82 3.4.1. Inhibition of PGFM........................................................................................................82 iii 3.4.2. Progesterone response to inhibiting PGF2α...................................................................83 3.4.3. Prolonged luteal activity ................................................................................................85 3.5. Conclusions ......................................................................................................................87 3.6. Acknowledgments ...........................................................................................................87 3.7. References ........................................................................................................................88 4. Hormonal, luteal, and follicular changes during initiation of persistent corpus luteum in mares ...................................................................................................................................94 Abstract ...................................................................................................................................95 4.1. Introduction .....................................................................................................................96 4.2. Materials and methods ...................................................................................................99 4.2.1. Mares..............................................................................................................................99 4.2.2. Protocol ..........................................................................................................................99 4.2.3. Hormone assays ...........................................................................................................100 4.2.4. Statistical analyses .......................................................................................................101 4.3. Results ............................................................................................................................101 4.4. Discussion.......................................................................................................................108 4.5. Conclusions ....................................................................................................................113 4.6. Acknowledgments .........................................................................................................113 4.7. References ......................................................................................................................114