Dose-dependent effects of a glucocorticoid on prolactin production.
Glucocorticoids are known to stimulate growth hormone (GH) production but to suppress prolactin (PRL) production. However, previous data were obtained with rather high doses of corticosterone. In this study we examined the effects of various doses (10 (-12) -10 (-7) M) of corticosterone on GH and PRL production in a rat pituitary somatomammotropic cell line, MtT/SM cells, and found that GH mRNA expression was facilitated by high doses (10 (-7) and 10 (-8) M). In contrast, a biphasic effect of corticosterone on PRL mRNA expression and secretion was observed, i.e., high doses (10 (-7) and 10 (-8) M) suppressed and low doses (10 (-12) -10 (-10) M) facilitated them. In an immunofluorescent staining study, the number of PRL immunopositive cells increased with low doses of corticosterone while it decreased with high doses of it, which corresponded to PRL mRNA expression and hormone secretion, respectively. These effects of corticosterone on PRL production were abolished by a glucocorticoid receptor (GR) antagonist, mifepristone. In addition, co-treatment with low doses of corticosterone (10 (-12) -10 (-10) M) and 17beta-estradiol (E(2), 10 nM) additively increased the number of PRL immunopositive cells. Moreover, a 24 h BrdU incorporation experiment suggested that the increase in the number of PRL immunopositive cells treated with low dose corticosterone was caused by novel synthesis of PRL while, on the other hand, that of those treated with E(2) resulted from PRL cell proliferation. Thus, we concluded that corticosterone biphasically regulates PRL production and the sensitivity of E(2) to different degrees.
Yokoyama
Kotaro
K
Graduate School of Science and Engineering, Saitama University, Sakura-ku, Saitama, Japan.
Hayashi
Mahoko
M
Mogi
Chihiro
C
Sasakawa
Yoshihiro
Y
Watanabe
Gen
G
Taya
Kazuyoshi
K
Devnath
Sukumar
S
Inoue
Kinji
K
D000818:Animals; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D003345:Corticosterone / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000494:pharmacology; D005938:Glucocorticoids / Q000494:pharmacology*; D013006:Growth Hormone / Q000378:metabolism; D006727:Hormone Antagonists / Q000494:pharmacology; D015735:Mifepristone / Q000494:pharmacology; D010902:Pituitary Gland / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D011388:Prolactin / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats
D005938:Glucocorticoids; D006727:Hormone Antagonists; D012333:RNA, Messenger; D015735:Mifepristone; D004958:Estradiol; D011388:Prolactin; D013006:Growth Hormone; D003345:Corticosterone