title: In vitro molecular assessment of the mechanisms of action of 19-nor progestins used as contragestational agents.
abstract: Norethisterone (NET) and levonorgestrel (LNG) are synthetic progestins used as contragestational agents. Both compounds are biotransformed at target tissues into A-ring reduced metabolites which possess different pharmacological properties. The aim of this study was to determine the molecular mechanisms of the progestational and antiprogestational effects of NET, LNG and their metabolites by using a highly efficient, sensitive in vitro molecular assay based on the detection of a reporter gene expression (the bacterial chloramphenicol acetyltransferase (CAT) inserted downstream of a minimal promoter containing two progesterone responsive elements (PRE2) and the TATA box. For this purpose we used CV-1 monkey kidney cells, which do not possess steroid receptors. These cells were cotransfected with a progesterone receptor expression vector and the reporter vector PRE2-TATA-CAT. Data obtained using this model showed that NET and LNG induced CAT activity in a manner similar to that of the potent progestin R5020. NET and LNG metabolites exhibited a weak progestational activity; however, when 5 alpha-NET metabolite was simultaneously administered with R5020, a clear antiprogestational effect similar to that of the antiprogestin RU486 was observed. Therefore, the results clearly demonstrate that the use of the reporter CAT vector containing hormone responsive elements is a suitable assay for the screening and evaluation of new synthetic steroids with agonist or antagonist progestational activities in transfected CV-1 cell line.
authors.affiliation: Departamento de Biología de la Reproducción, Instituto Nacional de la Nutrición S. Zubirán, Facultad de Química and FES-Zaragoza, Universidad Nacional Autónoma de México, México, D.F.
authors.forename: A M
authors.initials: AM
authors.lastname: Pasapera
authors.forename: I
authors.initials: I
authors.lastname: Camacho-Arroyo
authors.forename: J F
authors.initials: JF
authors.lastname: Savouret
authors.forename: G A
authors.initials: GA
authors.lastname: García
authors.forename: G
authors.initials: G
authors.lastname: Pérez-Palacios
authors.forename: C
authors.initials: C
authors.lastname: Pichon
authors.forename: M A
authors.initials: MA
authors.lastname: Cerbón
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D015500:Chloramphenicol O-Acetyltransferase / Q000378:metabolism*; D003280:Contraceptives, Oral, Synthetic / Q000494:pharmacology*; D000882:Haplorhini; D016912:Levonorgestrel / Q000494:pharmacology*; D009640:Norethindrone / Q000494:pharmacology*; D045167:Progesterone Congeners / Q000494:pharmacology*
chemical_list: D003280:Contraceptives, Oral, Synthetic; D045167:Progesterone Congeners; D016912:Levonorgestrel; D015500:Chloramphenicol O-Acetyltransferase; D009640:Norethindrone