title: Estrogen decreases the sensitivity of anterior pituitary to the inhibitory effect of nitric oxide on prolactin release.
abstract: OBJECTIVE
  We investigated the effect of chronic estrogen treatment on the inhibitory action of nitric oxide (NO) on prolactin release.
  
  
  METHODS
  The effect of NO on prolactin release was studied in anterior pituitaries of female Wistar rats, intact at random stages, ovariectomized (OVX), and OVX treated for 15 days with 17beta-estradiol (OVX-E(2)).
  
  
  RESULTS
  Sodium nitroprusside (NP, 0.5 mM), a NO donor, inhibited prolactin release from anterior pituitaries and was able to stimulate cGMP synthesis in intact and OVX rats. Only a high, supraphysiological concentration of NP (2 mM) inhibited prolactin release from anterior pituitaries of OVX-E(2) rats and increased cGMP synthesis in OVX-E(2) rats. 8-Br-cGMP, a cGMP analogue, decreased prolactin release from anterior pituitaries of OVX rats but did not affect it in OVX-E(2) rats.
  
  
  CONCLUSIONS
  Our results suggest that estrogen may modify the sensitivity of the anterior pituitary to the inhibitory effect of NO on prolactin release by affecting guanylyl cyclase activity and the cGMP pathway.
authors.affiliation: Centro de Investigaciones en Reproducción, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina.
authors.forename: Miguel Omar
authors.initials: MO
authors.lastname: Velardez
authors.forename: María
authors.initials: M
authors.lastname: del Carmen Díaz
authors.forename: Mercedes
authors.initials: M
authors.lastname: Lasaga
authors.forename: Ana María
authors.initials: AM
authors.lastname: Franchi
authors.forename: Beatriz Haydée
authors.initials: BH
authors.lastname: Duvilanski
mesh_terms: D000818:Animals; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D009569:Nitric Oxide / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D009599:Nitroprusside / Q000008:administration & dosage; D009994:Osmolar Concentration; D010052:Ovariectomy; D010903:Pituitary Gland, Anterior / Q000187:drug effects* / Q000378:metabolism*; D011388:Prolactin / Q000037:antagonists & inhibitors*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D009599:Nitroprusside; C016276:8-bromocyclic GMP; D009569:Nitric Oxide; D004958:Estradiol; D011388:Prolactin; D019001:Nitric Oxide Synthase; D006152:Cyclic GMP