RESUMEN
A single low dose administration of a high affinity anti-progestin agent like mifepristone during the early luteal phase inhibits blastocyst implantation in human and non-human primates. Though it has been observed that luteal phase serum concentrations of estradiol and progesterone were not affected by the application of anti-nidatory dose of early luteal phase mifepristone suggesting that ovarian steroidogenic function is not compromised, it is nevertheless possible that ovarian physiology at the local tissue level is affected in this treatment schedule. In the present study, healthy, mature, proven fertile female rhesus monkeys were divided into two groups. Group 2 animals were treated with a single dose of mifepristone (2 mg/kg body weight), while group 1 animals were injected with vehicle (1:4 benzoyl benzoate: olive oil, v/v, s.c.) on day 2 post-ovulation. The morphological examination including that of vascularity, as well as, histometric determination of profiles of immunopositivity for IL-1alpha and TGF-beta1 in stromal, follicular and luteal compartments of mid-luteal phase ovaries from animals with or without a single, anti-nidatory dose of mifepristone applied on day 2 after ovulation failed to reveal any significant change between the two groups. Thus, it appears that early luteal phase administration of a single antinidatory dose of mifepristone does not affect the ovarian physiology in the treatment cycle.