title: [Melatonin suppressing the proliferation of E2-induced pituitary prolactin-secreting tumor in rat involves the effects of estrogen receptor].
abstract: OBJECTIVE
  To investigate effects of melatonin on estrogen receptor at the primary stage of melatonin (MLT) inhibiting the proliferation of 17-beta-estradiol (E2)-induced pituitary prolactin-secreting tumor (prolactinoma) and its mechanisms in the rat.
  
  
  METHODS
  MLT inhibiting the proliferation of 17-beta-E2-induced prolactinoma was created by administrating different concentration of melatonin subcutaneously at 18:00 in every group of SD rat in vivo. We also examined the expression of MLT receptor in prolactinoma cells and the effects of MLT on the expression of estrogen receptor (ER) by in situ hybridization and the effects of MLT on the binding of ER to estrogen response element (ERE) by electrophoretic mobility shift assay (EMSA)in primary culture cells iv vitro.
  
  
  RESULTS
  The results showed that the weights of prolactinomas in MLT groups, in which 0.25 mg or 0.50 mg/day/rat melatonin was administrated subcutaneously at 18:00, were decreased significantly (P < 0.01 and P < 0.05). The expression of MLT1a and MLT1b were shown in pituitary prolactinoma cells. Compared with the prolactinoma, the expression of ER and the bind of ER to ERE in prolactinoma treated with 0.25 mg/day/rat or 0.50 mg/day/rat MLT was decreased (P < 0.01 and P < 0.01).
  
  
  CONCLUSIONS
  These data indicate that some dosage of MLT inhibit the development of E2-induced prolactinoma in SD rat. One of the mechanisms is involved in suppressing the expression of estrogen receptor and partly inhibiting the bind of ER to ERE.
authors.affiliation: Department of Physiology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100005, China.
authors.forename: Quan-Hui
authors.initials: QH
authors.lastname: Yang
authors.forename: Jian-Ning
authors.initials: JN
authors.lastname: Xu
authors.forename: Rong
authors.initials: R
authors.lastname: Zhang
authors.forename: Lie
authors.initials: L
authors.lastname: Gao
authors.forename: Rong-Kun
authors.initials: RK
authors.lastname: Xu
mesh_terms: D000818:Animals; D004958:Estradiol / Q000494:pharmacology*; D008297:Male; D008550:Melatonin / Q000494:pharmacology*; D010911:Pituitary Neoplasms / Q000473:pathology*; D015175:Prolactinoma / Q000473:pathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011960:Receptors, Estrogen / Q000187:drug effects; D020218:Response Elements
chemical_list: D011960:Receptors, Estrogen; D004958:Estradiol; D008550:Melatonin