Estrogen decreases the sensitivity of anterior pituitary to the inhibitory effect of nitric oxide on prolactin release.
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.
Velardez
Miguel Omar
MO
Centro de Investigaciones en Reproducción, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina.
del Carmen Díaz
María
M
Lasaga
Mercedes
M
Franchi
Ana María
AM
Duvilanski
Beatriz Haydée
BH
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
D009599:Nitroprusside; C016276:8-bromocyclic GMP; D009569:Nitric Oxide; D004958:Estradiol; D011388:Prolactin; D019001:Nitric Oxide Synthase; D006152:Cyclic GMP