Measurement of circulating corticotrophin-releasing factor in man

Abstract

A radioimmunoassay was developed to measure corticotrophin-releasing factor (CRF-41) extracted from human plasma using Vycor glass. Assay sensitivity was 20 ng/l and intra- and interassay coefficients of variation were 10.2 and 11.4% respectively. The normal range of plasma CRF-41 was less than 20-110 ng/l (n = 46). Plasma concentrations of CRF-41 in patients with Cushing's disease. Nelson's syndrome and Addison's disease were within the normal range. No correlation was found between CRF-41 and ACTH in these syndromes. Two patients with the ectopic ACTH syndrome had increased plasma concentrations of CRF-41. In normal subjects no changes in plasma CRF-41 occurred after insulin-induced hypoglycaemia, treatment with dexamethasone or feeding, and changes in the concentrations of CRF-41 did not reflect circadian changes in plasma concentrations of cortisol. Concentrations of immunoreactive CRF in plasma of women in the third trimester of pregnancy were increased (550-9300 ng/l) and gel filtration chromatography showed that this comprised CRF-41 and a higher molecular weight form. Reversed-phase high-performance liquid chromatography also revealed multiple peaks of immunoreactive CRF in extracts of plasma and placenta.

Corticotrophin‐Releasing Factor‐41 in the Human and Rat—Utility of a Highly Sensitive Enzyme Amplified Immunometric Assay

“…This also enables sequential addition of samples, antibody-enzyme conjugate and substrate allowing potentially interfering substances to be removed by washing (18). The ability of the assay to measure CRF-41 without the need for an extraction procedure is a significant improvement on RIA since differences in sample extraction have been implicated in the discrepancies between measurements?by different groups (8,9,19,20). The plasma Extracts were separated on a p-Bondapak C,, reverse-phase column using a gradient of 35% to 70% acetonitrile in 0.065% trifluoroacetic acid.…”

“…However, the RIA tcchnique is time consuming and can give elevated measurements in the presence of CRF-41 peptide fragments or peptides with dcgrees of sequence homology with CRF-41 (4). Such RIAs also 1-cquire extraction of the material from biological fluids to reduce interference (7)(8)(9). The development of a 'two-site' immunoradiometric assay (IRMA) for CRF-41 (10) was a significant advance, reducing interference from fragments and allowing direct measurement of the peptide in biological fluids including plasma (1 1) In this study, we sought to construct an enzyme amplified ilnmunometric assay (EAIA) for human/rat CRF-41 using two polyclonal antisera raised against the whole CRF-41 molecule.…”

The effect of modafinil on counter-regulatory and cognitive responses to hypoglycaemia

“…Arterialised plasma glucose was measured at the bedside using a glucose oxidase technique (Yellow Springs glucose analyzer; Yellow Springs Instruments, Yellow Springs, Ohio, USA). Plasma adrenaline and noradrenaline were measured by HPLC with electrochemical detection [26], glucagon [27], cortisol [28], growth hormone [29] and insulin [30] by a radioimmunoassay. Inter-and intra-assay variations were less than 10% for all assays.…”

The role of hepatic portal glucose sensing in modulating responses to hypoglycaemia in man

“…Plasma adrenaline and noradrenaline were measured by high performance liquid chromatography [26], glucagon [27], cortisol [28], growth hormone [29] and insulin [30] by a sensitive radioimmunoassay. Inter-assay and intra-assay variabilities were less than 10% for all assays.…”