Culture requirements for optimal expression of 1 alpha,25-dihydroxyvitamin D3-enhanced thyrotropin secretion.
An effect of the hormone, 1 alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3] on hormone secretion by normal rat pituitary cells was investigated in vitro. Based on previous findings using GH4C1 cells, dispersed anterior pituitary cell cultures were prepared and maintained in serum-free conditions for up to 6 d. Under these circumstances, there was no effect of 1,25(OH)2D3 to alter medium or cell-associated levels of thyrotropin (TSH), prolactin (PRL), or growth hormone (GH). Cultures maintained under these conditions had lower medium and cell-associated hormone levels and lesser responses to agonists than cultures maintained in serum-supplemented medium. In the presence of 10% charcoal-treated fetal bovine serum, treatment with 10(-8) M 1,25(OH)2D3 for 24 h selectively increased TRH (10(-10) to 10(-7) M)-induced TSH secretion (P less than 0.001), with maximal enhancement observed at 10(-9) M TSH-releasing hormone (TRH). Enhancement of TSH secretion by 1,25(OH)2D3 was detected after 15 min exposure to TRH. There was no effect on agonist-induced PRL or GH secretion or on cell-associated hormone levels. The effect was evident after 24 h treatment with 1,25(OH)2D3, and decreased thereafter. Several other steroid hormones had no effect on 10(-9) M TRH-induced TSH secretion. These data contrast with the effect of 1,25(OH)2D3 in GH cells. They suggest that 1,25(OH)2D3 may act selectively in the normal pituitary to modulate TSH secretion.
d'Emden
M C
MC
Department of Medicine, University of Melbourne, Royal Melbourne Hospital, Parkville, Victoria, Australia.
Wark
J D
JD
D000818:Animals; D002117:Calcitriol / Q000494:pharmacology*; D003470:Culture Media; D018492:Dopamine Antagonists; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D013006:Growth Hormone / Q000378:metabolism; D066298:In Vitro Techniques; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D011388:Prolactin / Q000378:metabolism; D051381:Rats; D012636:Secretory Rate / Q000187:drug effects; D013764:Tetrahydronaphthalenes / Q000494:pharmacology; D013972:Thyrotropin / Q000378:metabolism*; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology
D003470:Culture Media; D018492:Dopamine Antagonists; D013764:Tetrahydronaphthalenes; D004958:Estradiol; C011639:ADTN; D013973:Thyrotropin-Releasing Hormone; D011388:Prolactin; D013972:Thyrotropin; D013006:Growth Hormone; D002117:Calcitriol