Processing-independent radioimmunoanalysis: a general analytical principle applied to progastrin and its products |
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Authors: | L Bardram J F Rehfeld |
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Institution: | University Department of Gastroenterology C, Rigshospitalet, Copenhagen, Denmark. |
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Abstract: | Most peptide hormone assays measure only fully processed bioactive peptides. Such assays are unsuited to detect hormone gene expression by alternative or attenuated prohormone processing (tissue- or cell-specific processing). The gastrin system is expressed in several different tissues and is therefore useful for studies of tissue-specific processing. Consequently we have developed a simple processing-independent radioimmunoanalysis for progastrin. Using antisera against the NH2-terminus of a sequence, devoid of processing sites (preprogastrin76-86) after trypsination of neighboring cleavage sites, the assay quantitates the mRNA product irrespective of degree of processing. Used together with a conventional assay for the mature carboxyamidated gastrins, the processing-independent analysis shows that in different tissues only 1 to 55% of the total translation product is processed to bioactive gastrins. Thus processing-independent analysis greatly improves the detection of gastrin gene expression at the peptide level. The principle of the assay should be applicable to all protein and peptide systems. |
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