Adrenocorticotropin radioimmunoassay: properties of antisera against synthetic ACTH(1-24) and its clinical application.
Two antisera against synthetic ACTH(1-24) developed in rabbit showed strikingly different affinities toward the ACTH molecule. Both antisera (A-6 and A-7) were highly specific for the COOH-terminal region of ACTH(1-24). Antisera A-6 recognized ACTH(1-39) poorly. Radioimmunoassays (RIAs) using these antisera permitted the rapid (less than or equal to 18 h) quantitation of ACTH(1-24) (A-6) or ACTH(1-39) (A-7) at picogram levels. ACTH levels were determined on silicic acid extracts of rat and human plasma samples by the RIA specific for mid-region of ACTH(1-39) (A-7) and compared with that obtained by an ACTH(34-39) (C-terminal) RIA. In nearly all cases the C-terminal/mid-region ACTH ratios were less than 1.0, indicating that C-terminus of ACTH is more readily degraded by tissue or blood peptidases than are internal sequences. A solid-phase immunoadsorbent RIA specific for the extreme COOH-terminus of ACTH(1-24) was developed by coupling antiserum (A-6) to Sepharose 4B. This assay exhibited the same specificity as the soluble antiserum, yet tolerated relatively high concentrations of protein. Although the assay was suitable for rapid quantitation of ACTH(1-24), a decrease in sensitivity was observed in comparison to a conventional assay.
D000324:Adrenocorticotropic Hormone / Q000031:analogs & derivatives* / Q000097:blood* / Q000276:immunology; D000328:Adult; D000818:Animals; D000918:Antibody Specificity; D003366:Cosyntropin / Q000276:immunology*; D005260:Female; D006801:Humans; D008297:Male; D011817:Rabbits; D011863:Radioimmunoassay / Q000379:methods; D051381:Rats; D011919:Rats, Inbred Strains; D012824:Silicic Acid
D012824:Silicic Acid; D003366:Cosyntropin; D000324:Adrenocorticotropic Hormone