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Horm Metab Res 1972; 4(6): 477-481
DOI: 10.1055/s-0028-1094009
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© Georg Thieme Verlag KG Stuttgart · New York

Problems and Artefacts in ACTH Assay[*] [**]

H. L. Fehm , K. H. Voigt , E. F. Pfeiffer
  • Department of Endocrinology and Metabolism, Center of Internal Medicine and Pediatrics, University of Ulm, Germany
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Publication Date:
07 January 2009 (online)

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Abstract

Competitive "binding" of endogenous and exogenous ACTH (the latter in both labelled and unlabelled states) to silicates (QUSO G-32 and talcum) and to a varyingly active "binding factor" present in plasma was studied under several conditions. Whereas concentrations of ACTH were irrelevant, and no "binding" was observed to 5% bovine serum albumin in 0.9% saline, quantitative relations between the amounts of silicates and plasma volumes, respectively, and the percentage of ACTH adsorbed to the other competitor were established.

The "binding" phenomenon was also studied by means of gel filtration. Radiochromatography of ACTH-I125 incubated in plasma on Sephadex G-200 revealed a major peak of radioactivity located in a region with large molecular weight. "Binding" of ACTH was prevented by an excess of Ca++ - ions and by low pH-values. Whereas the physiological significance of the "binding" phenomenon remains obscure, it may well explain the difficulties of radioimmunological measurement of ACTH in untreated plasma.

Key words

ACTH - "Binding Factor" - Radioimmunoassay

1 Supported by Deutsche Forschungsgemeinschaft, Bad Godesberg, SFB 87/18/71

1 Supported by Deutsche Forschungsgemeinschaft, Bad Godesberg, SFB 87/18/71

2 Presented in part at the round table conference "ACTH in blood", 18th Symp. Dtsch.Ges. EndokrinoL, Hanover (Germany), March 1-4, 1972