Direct measurement of the precursors of adrenocorticotropin in human plasma by two-site immunoradiometric assay
An immunoradiometric assay (IRMA) for the direct measurement of the precursors of ACTH in unextracted human plasma has been developed and evaluated clinically in normal subjects and patients with disorders of the hypothalamic-pituitary-adrenal axis. The IRMA is based on an iodinated monoclonal antibody to ACTH and a monoclonal antibody to gamma MSH coupled to Sephacryl S300. The assay detects only peptides containing both epitopes, i.e. POMC (31K) and pro-ACTH (22K). The reference standard was partially purified POMC from culture medium of human corticotroph adenoma cells. The detection limit (greater than +2.5SD of the 0 standard) was 2.0 pmol/L and the within-assay coefficient of variation was less than 10% between 29 and 2600 pmol/L. Plasma concentrations of ACTH precursor peptides in 11 normal subjects sampled at 0930 h ranged from 5-34 pmol/L. The concentrations in the patient groups studied were: 260-2300 pmol/L in 5 patients with the ectopic ACTH syndrome associated with small cell lung cancer, less than 2.0-104 pmol/L in 10 patients with pituitary-dependent Cushing's disease, 23 pmol/L in a patient with Nelson's syndrome, and 3.0-230 pmol/L in 5 patients with Addison's disease. We conclude that this IRMA offers a simple and reliable method for measuring ACTH precursors in unextracted plasma. The proportionately greater elevation of ACTH precursors compared to ACTH in patients with the ectopic ACTH syndrome associated with small cell lung cancer but not in pituitary-dependent Cushing's syndrome, suggests that this assay may be clinically useful.
- Research Organization:
- Univ. of Manchester, Salford (England)
- OSTI ID:
- 6516961
- Journal Information:
- J. Clin. Endocrinol. Metab.; (United States), Vol. 67:6
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ADRENAL HORMONES
RADIOIMMUNOASSAY
ENDOCRINE DISEASES
DIAGNOSIS
CHROMATOGRAPHY
MONOCLONAL ANTIBODIES
NEOPLASMS
PATIENTS
PRECURSOR
ANTIBODIES
DISEASES
IMMUNOASSAY
IMMUNOLOGY
ISOTOPE APPLICATIONS
RADIOASSAY
RADIOIMMUNOLOGY
SEPARATION PROCESSES
TRACER TECHNIQUES
550601* - Medicine- Unsealed Radionuclides in Diagnostics