Characterization of natriuretic peptide receptor subtypes in the AtT-20 pituitary tumour cell line.
Receptors for the natriuretic peptide family have been characterized in the adrenocorticotrophic hormone (ACTH)-secreting AtT-20 pituitary tumour cell line. Northern blot analysis detected mRNA transcripts for the guanylate cyclase-linked GC-B receptor subtype. There was no evidence for the expression of either guanylate cyclase-linked GC-A receptor or atrial natriuretic peptide (ANP)-C (clearance) receptor mRNAs. Cyclic GMP production in AtT-20 cells was stimulated up to 200-fold by C-type natriuretic peptide (CNP), which was 10- and 20 times as effective as equivalent concentrations of brain natriuretic peptide and ANP respectively. Cyclic GMP dose-response curves to CNP failed to show any signs of saturation even at concentrations up to 30 microM, indicating a relatively low affinity of CNP for the GC-B receptor. Although CNP induced large stimulations in cyclic GMP production, specific binding of [125I-Tyr0]CNP could not be demonstrated in AtT-20 cells. The absence of specific binding with this radiolabelled analogue is possibly due to a reduced affinity for the GC-B receptor, as CNP analogues with N-terminal modifications such as [Tyr0]CNP and [127I-Tyr0]CNP exhibited reduced abilities to stimulate cyclic GMP production in these cells. Despite elevating cyclic GMP levels, CNP had no effect on basal or corticotrophin-releasing factor-stimulating ACTH release from the cells. These results show that the guanylate cyclase-coupled GC-B receptor is the only natriuretic peptide receptor subtype expressed in AtT-20 cells. Although CNP can markedly stimulate cyclic GMP production in these cells, there is incomplete expression of the normal natriuretic peptide-induced inhibitory pathway of ACTH secretion at some point distal to the production of cyclic GMP.
Gilkes
A F
AF
Molecular Endocrinology Group, School of Biological and Medical Sciences, University of St. Andrews, U.K.
Ogden
P H
PH
Guild
S B
SB
Cramb
G
G
D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000378:metabolism / Q000494:pharmacology*; D002460:Cell Line; D003346:Corticotropin-Releasing Hormone / Q000494:pharmacology; D006152:Cyclic GMP / Q000378:metabolism; D007700:Kinetics; D020098:Natriuretic Peptide, C-Type; D009419:Nerve Tissue Proteins / Q000378:metabolism / Q000494:pharmacology*; D010911:Pituitary Neoplasms / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D017461:Receptors, Atrial Natriuretic Factor / Q000096:biosynthesis / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D020098:Natriuretic Peptide, C-Type; D009320:Atrial Natriuretic Factor; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone; D017461:Receptors, Atrial Natriuretic Factor; D006152:Cyclic GMP