title: Vaginal keratinization during the estrous cycle in rats: a model for evaluating retinoid activity.
abstract: A model is described for evaluating the activity of a retinoid based on its effect on the keratinization of the vaginal epithelium that occurs on estrus (day 4) of a 4-day cycle in female rats. This keratinization process is dependent on the endogenous estradiol (E2) secreted between the evening of diestrus 2 (day 2) and that of proestrus (day 3). Various doses of all-transretinoic acid (tRA) were injected at different time points during the estrous cycle and the vaginal keratinization was assessed by microscope examination of unstained native or Papanicolaou-stained smear preparations. Additionally, the preovulatory E2 secretion was measured and ovaries were histologically examined. A single injection of 10 mg/kg tRA either on diestrus 2 (evening) or on proestrus (early morning) was able to induce a complete inhibition of the vaginal keratinization in more than 80% of the cases. This can be considered as a direct effect on the vaginal epithelial differentiation since neither the E2 secretion nor the ovulatory process were affected. The inhibition of vaginal keratinization can be used as a rapid and convenient in vivo model for screening retinoid candidates with antikeratinizing activity.
authors.affiliation: Institute of Histology, Faculty of Medicine, Strasbourg, France.
authors.forename: D
authors.initials: D
authors.lastname: Chateau
authors.forename: J M
authors.initials: JM
authors.lastname: Geiger
authors.forename: B
authors.initials: B
authors.lastname: Samama
authors.forename: N
authors.initials: N
authors.lastname: Boehm
mesh_terms: D000818:Animals; D004847:Epithelial Cells; D004848:Epithelium / Q000187:drug effects; D004958:Estradiol / Q000097:blood; D004971:Estrus / Q000502:physiology*; D005260:Female; D015603:Keratinocytes / Q000187:drug effects*; D007641:Keratolytic Agents / Q000494:pharmacology; D010053:Ovary / Q000187:drug effects / Q000648:ultrastructure; D010060:Ovulation / Q000187:drug effects; D011863:Radioimmunoassay; D051381:Rats; D017208:Rats, Wistar; D012176:Retinoids / Q000494:pharmacology*; D014212:Tretinoin / Q000494:pharmacology; D014621:Vagina / Q000187:drug effects* / Q000502:physiology
chemical_list: D007641:Keratolytic Agents; D012176:Retinoids; D004958:Estradiol; D014212:Tretinoin