Effects of bromocriptine on serum prolactin levels, pituitary weight and immunoreactive prolactin cells in estradiol-treated ovariectomized rats: an experimental model of estrogen-dependent hyperprolactinemia.
The present study was designed to assess the effects of bromocriptine, a dopamine agonist, on pituitary wet weight, number of immunoreactive prolactin cells and serum prolactin concentrations in estradiol-treated rats. Ovariectomized Wistar rats were injected subcutaneously with sunflower oil vehicle or estradiol valerate (50 or 300 micrograms/rat(-1) week (-1) for 2, 4, or 10 weeks. Bromocriptine (0.2 or 0.6 mg rat (-1) day (-1)) was injected daily during the last 5 or 12 days of estrogen treatment. Data were compared with those obtained for intact control rats. Administration of both doses of estrogen increased serum prolactin levels. No difference in the number of prolactin cells in rats treated with 50 micrograms estradiol valerate was observed compared to intact adult animals. In contrast, rats treated with 300 micrograms estradiol valerate showed a significant increase in the number of prolactin cells (P < 0.05). Therefore, the increase inn serum prolactin levels observed in rats treated with 50 micrograms estradiol valerate, in the absence of morphological changes in the pituitary cells, suggests a "functional" estrogen-induced hyperprolactinemia. Bromocriptine decreased prolactin levels in all estrogen-treated rats. The administration of this drug to rats previously treated with 300 micrograms estradiol valerate also resulted in a significant decrease in pituitary weight and number of prolactin cells when compared to the group treated with estradiol alone. The general antiprolactinemic and antiproliferative pituitary effects of bromocriptine treatment reported here validate the experimental model of estrogen-induced hyperprolactinemic rats.
Ribeiro
M F
MF
Departamento de Fisiologia, Universidade de Federal do Rio Grande do Sul, RS, Brasil.
Spritzer
P M
PM
Barbosa-Coutinho
L M
LM
Oliveira
M C
MC
Pavanato
M A
MA
Silva
I S
IS
Reis
F M
FM
D000818:Animals; D001971:Bromocriptine / Q000494:pharmacology*; D004958:Estradiol / Q000008:administration & dosage; D005260:Female; D006966:Hyperprolactinemia / Q000139:chemically induced*; D009929:Organ Size; D010052:Ovariectomy; D010902:Pituitary Gland / Q000187:drug effects* / Q000473:pathology*; D011388:Prolactin / Q000097:blood* / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar
D001971:Bromocriptine; D004958:Estradiol; D011388:Prolactin