Administration of antiprogestin J956 for contraception in bears: a pharmacological study.

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  • Additional Information
    • Source:
      Publisher: Elsevier Country of Publication: United States NLM ID: 0421510 Publication Model: Print Cited Medium: Print ISSN: 0093-691X (Print) Linking ISSN: 0093691X NLM ISO Abbreviation: Theriogenology Subsets: MEDLINE
    • Publication Information:
      Publication: [New York, N.Y.?] : Elsevier
      Original Publication: Los Altos, Calif., Geron-X.
    • Subject Terms:
      Contraceptive Agents, Female/*pharmacology ; Progestins/*antagonists & inhibitors ; Ursidae/*physiology; Administration, Oral ; Animals ; Biological Availability ; Contraceptive Agents, Female/administration & dosage ; Contraceptive Agents, Female/blood ; Female ; Injections, Intramuscular/veterinary ; Pregnancy ; Receptors, Progesterone/antagonists & inhibitors ; Receptors, Progesterone/metabolism ; Ursidae/blood ; Ursidae/metabolism
    • Abstract:
      Effective and reversible control of reproduction in bears is highly desirable for conservation and management programs in zoos to establish genetically variable ex-situ populations of bears within the constraints of limited space in captivity. The reproductive physiology of bears is characterized by two main traits--seasonality and delayed implantation, which is progesterone dependent. This offers the opportunity to interrupt early pregnancy by short-term administration of antiprogestins. The aim of the present study was to investigate the pharmacological characteristics of antiprogestin J956 to establish an efficient contraceptive protocol for administration of J956 in captive bears. The J956 binds to the uterine progesterone receptor of bears (n = 2) with almost the same relative binding affinity (1.25) as progesterone. The blood serum level of J956 after oral (on four consecutive days) and single parenteral administration was determined by a modified progestin receptor assay. The relative bioavailability of J956 after oral administration was approximately 10% of the parenteral administration. The estimated half-life was 12 to 16 hours after oral administration. Parenteral treatment of J956 (10 mg/kg body mass) led to sustain plasma concentrations (6.4 +/- 1.3 ng/mL) in one black bear and in five brown bears. The plasma level lasted for almost 2 months. Oral and low dosage parenteral (1 mg/kg body mass) administration of J956 had no effect on ongoing pregnancies in bears. Whereas single parenteral administration with higher dosages of J956 (7.5 to 10 mg/kg body mass) efficiently prevented implantation of early embryos in eight female captive bears.
    • Accession Number:
      0 (Contraceptive Agents, Female)
      0 (Progestins)
      0 (Receptors, Progesterone)
    • Publication Date:
      Date Created: 20010927 Date Completed: 20011204 Latest Revision: 20190822
    • Publication Date:
      20231215
    • Accession Number:
      10.1016/s0093-691x(01)00592-1
    • Accession Number:
      11572441