A sensitive radioimmunoassay for corticotropin using a fully biologically active 125I-labeled ligand
The human corticotropin (ACTH) analog, Phe2,Nle4-ACTH-(1-38) was iodinated by the chloramine-T procedure and the product was purified by reverse phase high performance liquid chromatography. The specific radioactivity of (/sup 125/I)Tyr23,Phe2,Nle4-ACTH-(1-38) was determined by comparing the antiserum binding curves of the iodinated peptide and (3H)ACTH of known specific activity. This method gave a value of 1800 +/- 75 Ci/mmol, which is close to the theoretical radioactivity expected for the introduction of a single /sup 125/I atom into the peptide. (/sup 125/I)Tyr23,Phe2,Nle4-ACTH-(1-38) was as potent as ACTH in stimulating corticosterone production in isolated rat adrenocortical cells. The concentrations for half-maximal steroidogenesis were 36.5 +/- 6.1 pM for the /sup 125/I derivative and 37.6 +/- 6.7 pM for ACTH. By the use of this /sup 125/I-labeled ligand, a highly sensitive RIA capable of detecting 1 pg ACTH was developed.l The antiserum employed in this study appeared to be directed against residues 11-13 of ACTH.
- OSTI ID:
- 5614679
- Journal Information:
- Endocrinology; (United States), Vol. 109:1
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
ACTH
RADIOIMMUNOASSAY
BIOCHEMICAL REACTION KINETICS
CORTICOSTEROIDS
IMMUNE SERUMS
IODINE 125
LABELLED COMPOUNDS
LIGANDS
TRITIUM COMPOUNDS
ADRENAL HORMONES
BETA DECAY RADIOISOTOPES
DAYS LIVING RADIOISOTOPES
ELECTRON CAPTURE RADIOISOTOPES
HORMONES
HYDROXY COMPOUNDS
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KETONES
KINETICS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
PEPTIDE HORMONES
PITUITARY HORMONES
PREGNANES
RADIOASSAY
RADIOISOTOPES
REACTION KINETICS
STEROID HORMONES
STEROIDS
TRACER TECHNIQUES
550601* - Medicine- Unsealed Radionuclides in Diagnostics
550201 - Biochemistry- Tracer Techniques