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ACTH

Thursday 23 February 2006

IHCDB

Definition: Corticotropin (ACTH) is synthesized by the anterior pituitary gland and stimulates the adrenal cortex.

Structure

Human ACTH has a molecular weight of 4,541 and contains 39 amino acids (Lee et al., 1961).

ACTH has structural similarities to melanotropin (melanocyte-stimulating hormone) (alpha-MSH). Human beta-melanotropin (beta-MSH) has 22 amino acid residues and a molecular weight of 2,661.

Work on the structure of the ACTH gene by restriction enzyme techniques showed that 6 hormones are derived from one gene: ACTH, lipotropin, alpha-MSH, beta-MSH, endorphin, and one other.

Thus, extensive amino acid differences between these hormones were not adequate evidence for their being distinct.

ACTH and beta-lipotropin (beta-LPH) are derived from a large precursor peptide produced by gene POMC.

Each of these hormones is known to include smaller peptides having distinct biologic activities: alpha-melanotropin (alpha-MSH) and corticotropin-like intermediate lobe peptide (CLIP) are formed from ACTH; gamma-LPH and beta-endorphin are peptide components of beta-LPH.

Beta-MSH is contained within gamma-LPH. The precursor peptide was called proopiomelanocortin (POMC) in 1979.

Immunochemistry

- The 02A3 antibody from Dako Is specific for the C-terminal sequence of ACTH (ACTH 24-39) and was found not to cross-react with ╬▓LPH by radioimmunoassay. The antibody labels corticotrophs in the adenohypophysis. It may be useful in the classification of pituitary adenomas and in the differential diagnosis of primary and metastatic tumors of the pituitary.