RESUMO
Nuclear diameter, DNA synthesis, and mitotic index in the pituitary cells of male rats and serum prolactin were measured after a period of 8 days of treatment with a dopamine agonist and an antagonist given with and without estrogen. In the absence of estrogen, the dopamine agonist, bromocriptine, diminished the mean nuclear diameter of the pituitary cells and lowered pituitary DNA synthesis, and the dopamine-blocking agent haloperidol had no effect. Estrogen increased the mean nuclear diameter, pituitary mitotic index, and DNA synthesis. Bromocriptine prevented the estrogen-induced increase in mean nuclear diameter and pituitary DNA synthesis and mitotic index were lowered. Haloperidol augmented the estrogen-induced increase in mean nuclear diameter, pituitary DNA synthesis, and mitotic index. Positive correlations were obtained between mean nuclear diameter and DNA synthesis and serum prolactin. It was concluded that nuclear diameter was influenced by both DNA synthesis and secretory activity in pituitary cells.
Assuntos
Bromocriptina/farmacologia , Núcleo Celular/ultraestrutura , Dietilestilbestrol/análogos & derivados , Haloperidol/farmacologia , Adeno-Hipófise/ultraestrutura , Animais , Núcleo Celular/efeitos dos fármacos , Núcleo Celular/fisiologia , Replicação do DNA/efeitos dos fármacos , Dietilestilbestrol/farmacologia , Masculino , Índice Mitótico/efeitos dos fármacos , Adeno-Hipófise/efeitos dos fármacos , Adeno-Hipófise/fisiologia , Ratos , Ratos EndogâmicosRESUMO
The times of onset of oestrogen-induced prolactin secretion and DNA synthesis were studied in the pituitary gland of the male rat. At intervals from 3 to 96 h after injection of 10 mg diethylstilboestrol dipropionate, serum and pituitary prolactin concentrations were measured by radioimmunoassay and pituitary DNA synthesis by incorporation of [3H]-thymidine in vitro. Serum prolactin was raised significantly from 6 h onwards and DNA synthesis was increased from 30 h onwards. Pituitary prolactin concentration began to increase at 30 h. Significant correlations were obtained between serum prolactin and DNA synthesis from 24 to 72 h but not during the period of prolactin secretion from 6 to 24 h.
Assuntos
DNA/biossíntese , Dietilestilbestrol/análogos & derivados , Hipófise/metabolismo , Prolactina/metabolismo , Animais , Dietilestilbestrol/farmacologia , Masculino , Hipófise/efeitos dos fármacos , Prolactina/sangue , Ratos , Fatores de TempoRESUMO
Haloperidol, bromocriptine and diethylstilboestrol dipropionate were given in various régimes to male rats to determine their effects on pituitary DNA synthesis, prolactin secretion and growth hormone secretion. Haloperidol increased serum prolactin but did not stimulate pituitary DNA synthesis or reduce pituitary prolactin concentrations. Haloperidol potentiated the effects of oestrogen on serum prolactin and on pituitary DNA synthesis; pituitary prolactin concentrations were greatly reduced, and growth hormone secretion was slightly inhibited. The inhibitory effects of bromocriptine in oestrogen-stimulated rats were demonstrated by smaller pituitary weights and decreased DNA synthesis; serum prolactin levels were lowered and pituitary prolactin concentrations were increased. Haloperidol, given to rats treated with oestrogen and bromocriptine, reversed the inhibitory effects of bromocriptine on DNA synthesis and serum prolactin; pituitary prolactin concentrations fell to well below normal. The results suggest that the haloperidol potentiation of oestrogen-induced pituitary DNA synthesis may depend upon stimulation of prolactin secretion together with reduction of intracellular prolactin levels.