The effect of the anti-progestin ru 486 on early pregnancy in the long-tailed macaque (Macaca fascicularis)

George E O Owiti, Alice F Tarantal, Bill L. Lasley, Andrew G Hendrickx

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


The efficacy of various doses of RU 486 in terminating pregnancy before and after the luteal-placental shift (LPS) in the long-tailed macaque (Macaca fascicularis) was assessed through sonographic examination and measurements of steroid hormones and their metabolites. Intramuscular injection of 1.0, 2.5,12.5, or 25.0 mg/kg was administered either from gestational day (GD) 15-18 (Group 1; N = 11) or GD 23-26 (Group 2; N = 9). The timing of treatment was determined by the detection of the preovulatory estrogen peak via daily urinary estrone conjugate (E1C) measurements. In Group 1, a 90.9% pregnancy loss was observed ( 10 11); seven animals aborted during GD 15-20, two animals indicated early embryonic death with retained gestational sacs, one animal aborted on GD 56, and one pregnancy was maintained. In Group 2, an 88.9% pregnancy loss was observed ( 8 9); eight animals aborted between GD 26-29, and one pregnancy was unaffected. Hormone profiles appeared to fall secondarily to the loss of trophoblast function. These results indicate: (a) RU 486 was more effective after the LPS; and (b) the primary effect of RU 486 appeared to be at the level of the products of conception.

Original languageEnglish (US)
Pages (from-to)201-211
Number of pages11
Issue number2
StatePublished - 1989

ASJC Scopus subject areas

  • Medicine(all)
  • Obstetrics and Gynecology


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