Prolactin Secretion from Clonal Pituitary Cells following Incubation with Estradiol, Progesterone, Thyrotrophin Releasing Hormone and Dopamine

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Abstract
Prolactin (PRL) release was assessed using clonal cells from the 2B8 strain [rat fetus] grown in the presence of estradiol (sodium sulfate) (E2), progesterone (P), thyrotropin-releasing hormone (TRH) and/or dopamine hydrochloride (DA). Using concentrations of E2 ranging from 10-11 M-10-6 M, it was found that a significant amount of PRL was released with doses of 10-10 M-10-8 M. No effect was observed with either higher or lower concentrations of the steroid. Approximately the same amount of PRL was released from pituitary cells incubated with 2 .times. 10-9 M TRH as was noted with 10-8 M E2. When these 2 secretagogues were combined, significantly more PRL was present in the medium than when either was employed alone. Prolactin release was significantly inhibited from cells cultured with 10-7 M-10-5 M DA; lower concentrations were either ineffective or were found to stimulate PRL secretion. In combination with 10-8 M E2 or 2 .times. 10-9 M TRH, 10-6 M DA significantly reduced the stimulatory effect of either of these 2 compounds. When E2 and TRH were incubated together in the presence of DA, less of an inhibition of PRL was noted than when DA was combined with either E2 or TRH. Inhibition of PRL release also occurred when the cells were incubated with 10-11 M-10-6 M P. The stimulatory effect of 10-8 M E2 was found to be suppressed by 10-6 M P. The 2B8 clonal strain is sensitive to agents known to affect PRL secretion in vivo.

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