The proopiomelanocortin (POMC) gene expression of AtT20 mouse pituitary cells is dependent on cell culture conditions.
We have compared the properties of AtT20 cells cultivated in a Dulbecco's modified Eagles medium containing 10% fetal calf serum (FCS) and of AtT20 cells adapted to a chemically better defined medium with transferrin, albumin, insulin, sodium selenit and 0.2% FCS. Our interest was focused on the hypothalamo-pituitary-adrenal axis (HPA) involved adrenocorticotropic hormone (ACTH) and the potent opioid peptide beta-endorphin (beta-END). There were no differences in basal secretion of ACTH and beta-END by cells cultivated in medium containing 10% or 0.2% serum, respectively. In combination to the decreased proliferation activity of AtT20 cells, grown in the serum-reduced medium we found a strongly enhanced ACTH secretion activity stimulated by the corticotropin releasing hormone (CRH) in contrast to normally cultivated AtT20 cells (10% serum). In addition, the proopiomelanocortin (POMC) gene expression was significantly down regulated in serum-reduced medium and was normalized again after further cultivation in a 10% serum containing medium. This leads to the conclusion that under standard conditions (10% serum) the gene transcription is increased by hitherto uncharacterized modulators present in the serum. The unexpected unchanged amounts of ACTH and beta-End could be the result of increased protein convertases activities. These enzymes are responsible for the POMC precursor processing into beta-End and ACTH.
Fickel
J
J
Research Institute of Molecular Pharmacology, Res. Group Cell. and Biochem. Pharmacology, Berlin, FRG.
Savoly
S
S
Vogel
U
U
Furkert
J
J
Melzig
M
M
D000818:Animals; D015152:Blotting, Northern; D002455:Cell Division; D002460:Cell Line; D003470:Culture Media; D005786:Gene Expression Regulation; D051379:Mice; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000378:metabolism*; D011333:Pro-Opiomelanocortin / Q000235:genetics*
D003470:Culture Media; D011333:Pro-Opiomelanocortin