THE PROSTAGLANDINS: BASIC CHEMISTRY AND ACTION

THE PROSTAGLANDINS: BASIC CHEMISTRY AND ACTION

1. CLASSIFICATION AND NOMENCLATURE

   • Derived from essential fatty acids
     • Thromboxanes
     • Leukotrienes
   • constitute a unique class of polyunsaturated, hydroxylated, 20-carbon fatty acids categorized as eicosanoids
   • 1 series
     • One double bond
     • Derived from dihomo-γ-linolenic acid
   • 2 series
     • Two double bonds
     • Derived from arachidonic acid
   • 3 series
     • Three double bonds
     • Derived from eicosapentaenoic acid

2. BIOSYNTHESIS AND METABOLISM

   • Formed in a substrate-limiting environment
   • Rapidly metabolized
   • Eicosanoid precursor substrates
     • Fatty acids
       • Cholesteryl esters
       • Phospholipids
       • Triglycerides
   • Lipoxygenase Pathway
     • Lipoxygenase products
     • Hydroperoxyeicosatetraenoic acids
     • Leukotrienes
   • Prostaglandin Synthetase Pathway
     • Incorporates molecular oxygen into arachidonic acid
       • Prostaglandin endoperoxides
         • Rapidly metabolized in the lung
     • Prostaglandin cyclooxygenase
       • Inhibit prostaglandin biosynthesis

3. ACTIONS OF PROSTAGLANDINS

   • Role of Prostaglandins in Gonadotropin Secretion
     • Effect that appears to be mediated by an action at the level of the hypothalamus
   • Ovulation and Prostaglandins
     • Ovarian follicular ruptura process
     • Follicular prostaglandin formation during ovulation
       • Dependent on gonadotropins
   • Role of Prostaglandins in Luteal Function: Luteolysis and Menstruation
     • PGF induces functional regression of the corpus luteum
       • Receptor-mediated process
   • Prostaglandins in the Uterus
     • Nonpregnant endometrium
       • PGF
       • PGE
     • Synthesis of prostaglandins is greater
       • Glandular epithelium than in the stroma of the endometrium
       • During the secretory phase than during the proliferative phase
   • Prostaglandins and Parturition
     • Potent stimulators of uterine contractility
     • Induce cyclic contractions of the gravid uterus
     • Early labor and abortion
   • Prostaglandins and the Ductus Arteriosus
     • Controlling ductus arteriosus patency at term

4. POTENTIAL PARALLEL ROLES OF OXYGEN RADICALS AND EICOSANOIDS IN REPRODUCTION

   • Reactive oxygen species
     • Physiologic role in reproduction
     • Singlet oxygen
     • Superoxide anion
     • Hydrogen peroxide
     • Hydroxyl radical
     • Produced in
       • Reproductive system
       • Endothelial cells

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