title: Effects of anti-estrogens on early pregnancy in guinea pigs.
abstract: OBJECTIVE
  To compare effects of various anti-estrogens on early pregnancy.
  
  
  METHODS
  Fifty regularly cycling guinea pigs were divided into five groups (five animals/group), of which three groups received 3 mg/kg body weight Nafoxidine, Centchroman, or Tamoxifen, respectively, on the 1st, 2nd, or 3rd day of pregnancy. The rest of the animals were kept as controls, and received either saline or propylene glycol. Autopsies were done on the 8th day of pregnancy in all the groups. Presence or absence of implantation sites was observed by using a stereomicroscope. Plasma levels of 17 beta-estradiol and progesterone and their receptors, as well as enzyme levels in the uterine tissue, were estimated.
  
  
  RESULTS
  During normal early pregnancy there was an increase in the concentration of peripheral plasma levels of steroid hormones with respect to enzyme and steroid hormone receptor levels in the uterus. Administration of anti-estrogens showed a decreased trend in all the variables studied, especially in the tamoxifen-treated animals.
  
  
  CONCLUSIONS
  The results of the study suggest that anti-estrogens, if administered during early pregnancy, can prevent the process of ovum implantation in this species.
authors.affiliation: Department of Reproductive Biomedicine, National Institute of Health and Family Welfare, New Delhi, India.
authors.forename: M S
authors.initials: MS
authors.lastname: Wisel
authors.forename: J K
authors.initials: JK
authors.lastname: Datta
authors.forename: R N
authors.initials: RN
authors.lastname: Saxena
mesh_terms: D000818:Animals; D002402:Cathepsin D / Q000032:analysis / Q000096:biosynthesis; D002486:Centchroman / Q000494:pharmacology; D010064:Embryo Implantation / Q000187:drug effects*; D004958:Estradiol / Q000032:analysis / Q000096:biosynthesis; D004965:Estrogen Antagonists / Q000494:pharmacology*; D005260:Female; D006168:Guinea Pigs; D007783:Lactones / Q000032:analysis; D007931:Leucyl Aminopeptidase / Q000032:analysis / Q000096:biosynthesis; D009256:Nafoxidine / Q000494:pharmacology; D009929:Organ Size; D010741:Phospholipases A / Q000032:analysis / Q000096:biosynthesis; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000187:drug effects*; D011374:Progesterone / Q000032:analysis / Q000096:biosynthesis; D011959:Receptors, Estradiol / Q000032:analysis / Q000096:biosynthesis; D011980:Receptors, Progesterone / Q000032:analysis / Q000096:biosynthesis; D013629:Tamoxifen / Q000494:pharmacology; D014599:Uterus / Q000033:anatomy & histology / Q000187:drug effects* / Q000201:enzymology
chemical_list: D004965:Estrogen Antagonists; D007783:Lactones; D011959:Receptors, Estradiol; D011980:Receptors, Progesterone; D013629:Tamoxifen; D002486:Centchroman; D011374:Progesterone; D009256:Nafoxidine; D004958:Estradiol; D010741:Phospholipases A; D007931:Leucyl Aminopeptidase; D002402:Cathepsin D