Corticotropin-releasing (CRH) activity of thymic peptides on CRH-insensitive corticotropic tumor cells.
A number of thymic preparations are known to stimulate corticotropin (ACTH) release from pituitary cells but it remains unclear whether this effect is mediated by the corticotropin-releasing hormone (CRH) receptor-associated pathway. We report here that thymosin fraction five (TF5), peptide MB-35 and possibly calf thymus histones can stimulate the release of ACTH from a CRH-insensitive variant of the mouse corticotropic cell line AtT20. The effective concentration range at which TF5 and MB-35 displayed their ACTH-releasing activity in a dose-dependent manner was 100 to 2,000 micrograms/ml and 10 to 100 ng/ml, respectively, whereas neither preparation induced a significant depletion of intracellular ACTH stores. Our data suggest that thymosin peptides can stimulate ACTH release from corticotrophs by a CRH receptor-independent mechanism.
Goya
R G
RG
Department of Biochemistry and Physiology, University of Reading, United Kingdom.
Castro
M G
MG
Hannah
M J
MJ
Sosa
Y E
YE
Lowry
P J
PJ
D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000704:Analysis of Variance; D000818:Animals; D003346:Corticotropin-Releasing Hormone / Q000378:metabolism*; D015592:Immunoradiometric Assay; D036341:Intercellular Signaling Peptides and Proteins; D051379:Mice; D009842:Oligopeptides / Q000494:pharmacology*; D010455:Peptides / Q000494:pharmacology*; D013947:Thymosin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D013953:Thymus Neoplasms / Q000378:metabolism*; D014407:Tumor Cells, Cultured / Q000378:metabolism
D036341:Intercellular Signaling Peptides and Proteins; D009842:Oligopeptides; D010455:Peptides; C033782:thymosin fraction 5; C064563:thymic humoral factor gamma 2; C067684:peptide MB-35; D013947:Thymosin; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone