Estrogen modulates neuromedin B effects on thyrotropin and prolactin release in vitro.
Neuromedin B(NB), a bombesin-like peptide, has been shown to inhibit thyrotropin (TSH) release in pituitary explants of male rats and to stimulate Prolactin (PRL) release in male pituitary cell cultures. We investigated the effect of estrogen status of female rats on the response of thyrotrophs and lactotrophs to neuromedin B (NB) in vitro. Ovariectomized rats were treated with near-physiological or high doses of 17beta estradiol benzoate (0.7 or 14 EB microg/100 gBW/daily, 10 days) or with vehicle (OVX). EB treatment induced a dose-dependent increase in serum prolactin and an increase in pituitary NB content, measured by specific RIA, that was similar in both EB groups (P < 0.05). TSH release from isolated hemipituitaries of OVX rats was significantly reduced (P < 0.05) in the presence of 10(-7) M NB. OVX + EB0.7 glands responded to NB with a not statistically significant dose-dependent decrease in TSH release. However, glands from hyperestrogenized rats (OVX + EB14) required a higher dose (10(-5) M) of NB to inhibit TSH release (P < 0.05). PRL release was highly increased (p < 0.001) by the presence of 10(-5) M NB only in glands of hyperestrogenized rats, while no effect of NB was observed in the other groups. In conclusion, estrogen status of female rats modulates the inhibitory effect of NB on TSH release in vitro and hyperestrogenism is required for stimulatory effect of NB on PRL release in vitro. It is suggested that the induction of PRL release by neuromedin B is a pharmacological rather than a physiological effect, but neuromedin B may contribute to the increased release of PRL associated with hyperestrogenism.
Moreira
Rachel Moraes
RM
Laboratório de Endocrinologia Molecular, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, CCS, Bloco G, Ilha do Fundão, Rio de Janeiro 21949-900, Brazil.
Curty
Flavio Henrique
FH
Lisboa
Patricia Cristina
PC
Amaral
Daniele
D
Ortiga-Carvalho
Tania Maria
TM
Pazos-Moura
Carmen C
CC
D000818:Animals; D004305:Dose-Response Relationship, Drug; D004336:Drug Antagonism; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology*; D005260:Female; D066298:In Vitro Techniques; D015287:Neurokinin B / Q000031:analogs & derivatives* / Q000378:metabolism*; D010052:Ovariectomy; D010903:Pituitary Gland, Anterior / Q000187:drug effects* / Q000378:metabolism; D011388:Prolactin / Q000378:metabolism*; D011863:Radioimmunoassay; D051381:Rats; D013972:Thyrotropin / Q000378:metabolism*
C074283:estradiol 3-benzoate; D004958:Estradiol; D015287:Neurokinin B; C038393:neuromedin B; D011388:Prolactin; D013972:Thyrotropin