title: Radioimmunoassay of corticotropin from plasma.
abstract: We describe a specific and highly sensitive radioimmunoassay for corticotropin (ACTH) in human plasma. As little as 1.9 pg of circulating ACTH can be detected per milliliter (0.44 pmol/L). ACTH is first extracted from plasma samples by adsorption onto pretreated Vycor glass powder, eluted from the adsorbent by acetone, and then lyophilized. For purification of 125I-labeled ACTH, a small octadecasilyl silica column is used. The mean (and SD) concentration of ACTH in plasma from 18 ostensibly normal subjects was 10.3 (4.3) pmol/L. After overnight suppression with dexamethasone in seven of these normal subjects, their ACTH values fell to 2.62 (1.3) pmol/L (p less than 0.0005). This assay will permit clinical evaluation of ACTH plasma concentrations in clinical investigation and of the effects of drug administration on circulating ACTH.
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000097:blood*; D000327:Adsorption; D003429:Cross Reactions; D003907:Dexamethasone; D005898:Glass; D006801:Humans; D007457:Iodine Radioisotopes; D007553:Isotope Labeling; D011863:Radioimmunoassay / Q000379:methods*; D012016:Reference Values
chemical_list: D007457:Iodine Radioisotopes; D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone