title: Identification of adrenocorticotropin receptor messenger ribonucleic acid in the human pituitary and its loss of expression in pituitary adenomas.
abstract: The ACTH receptor (ACTH-R) is the second member of the melanocortin (MC-2) receptor family that includes five seven-transmembrane G protein-coupled receptors and has been shown to be predominantly expressed in the adrenal cortex. It has been postulated that ACTH may regulate its own secretion through ultra-short-loop feedback within the pituitary. ACTH-secreting adenomas are characterized by resistance to glucocorticoid feedback, and they may have dysregulated ACTH feedback. We therefore investigated the ACTH-R in normal and adenomatous human pituitary tissue. We report here the identification of ACTH-R mRNA in the human pituitary gland, which was confirmed by direct sequencing. We studied the expression of the ACTH-R in 23 normal pituitary specimens and 53 pituitary adenomas (22 ACTH-secreting, nine GH-secreting, eight prolactin-secreting, one TSH-secreting, one FSH-secreting, 10 nonfunctioning, and two silent corticotroph adenomas), using the sensitive technique of real-time quantitative PCR. Contamination of ACTH-secreting adenomas and nonfunctioning pituitary adenomas with nonadenomatous tissue was excluded by lack of Pit-1 expression. ACTH-R mRNA was detected in all normal pituitary specimens, and in situ hybridization colocalized expression to ACTH staining cells only. However, ACTH-R mRNA levels were undetectable in 16 of 22 ACTH-secreting tumors and in both silent corticotroph tumors. Diagnostic preoperative plasma ACTH levels were significantly lower in the ACTH-R positive ACTH-secreting tumors, compared with those who were ACTH-R negative (P = 0.0006). Direct sequencing of the coding region of the ACTH-R in cDNA from three ACTH-secreting tumors positively expressing the receptor showed no mutations, as did sequencing of genomic DNA in three receptor negative ACTH-secreting tumors and the two silent corticotrophs. These results provide further evidence compatible with an ACTH feedback loop in the pituitary and suggest that loss of expression of the ACTH-R in corticotroph adenomas of patients with Cushing's disease may play a role in the resistance to feedback of the pituitary-adrenal axis seen in these patients.
authors.affiliation: Department of Endocrinology, St Bartholomew's Hospital, London EC1A 7BE, United Kingdom.
authors.forename: Damian G
authors.initials: DG
authors.lastname: Morris
authors.forename: Blerina
authors.initials: B
authors.lastname: Kola
authors.forename: Ninetta
authors.initials: N
authors.lastname: Borboli
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Kaltsas
authors.forename: Maria
authors.initials: M
authors.lastname: Gueorguiev
authors.forename: Anne Marie
authors.initials: AM
authors.lastname: McNicol
authors.forename: Roderick
authors.initials: R
authors.lastname: Ferrier
authors.forename: T Hugh
authors.initials: TH
authors.lastname: Jones
authors.forename: Stephanie
authors.initials: S
authors.lastname: Baldeweg
authors.forename: Michael
authors.initials: M
authors.lastname: Powell
authors.forename: Sándor
authors.initials: S
authors.lastname: Czirják
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Hanzély
authors.forename: Jan-Ove
authors.initials: JO
authors.lastname: Johansson
authors.forename: Márta
authors.initials: M
authors.lastname: Korbonits
authors.forename: Ashley B
authors.initials: AB
authors.lastname: Grossman
mesh_terms: D000236:Adenoma / Q000378:metabolism*; D000293:Adolescent; D000324:Adrenocorticotropic Hormone / Q000097:blood; D000328:Adult; D000368:Aged; D002648:Child; D018076:DNA, Complementary / Q000235:genetics; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008297:Male; D008875:Middle Aged; D010902:Pituitary Gland / Q000378:metabolism*; D010911:Pituitary Neoplasms / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D011333:Pro-Opiomelanocortin / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D018043:Receptors, Corticotropin / Q000235:genetics* / Q000378:metabolism; D014018:Tissue Distribution
chemical_list: D018076:DNA, Complementary; D012333:RNA, Messenger; D018043:Receptors, Corticotropin; D011333:Pro-Opiomelanocortin; D000324:Adrenocorticotropic Hormone