Ornithine decarboxylase assay in human colorectal mucosa. Methodologic issues of importance to quality control
✍ Scribed by Harinder S. Garewal; Donna Sloan; Richard E. Sampliner; Brian Fennerty
- Publisher
- John Wiley and Sons
- Year
- 1992
- Tongue
- French
- Weight
- 449 KB
- Volume
- 52
- Category
- Article
- ISSN
- 0020-7136
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✦ Synopsis
Abstract
Ornithine decarboxylase may be a useful biomarker for risk of neoplasia in colorectal tissues. Investigators have reported enzyme activities varying by as much as 10‐ to 20‐fold using variations of the usual ^14^CO~2~ release assay. We have examined the effect of different methodologic factors on calculated ornithine decarboxylase activity. Major effects on the assay result (>20% change) were produced by: (I) use of Tris vs. phosphate buffer, the former yielding 1.5‐ to 4‐fold greater activity; (2) protein content of the reaction mixture with significant error if <50 μg; (3) use of α‐difluoro‐methylornithine‐inhibited blank versus buffer‐only blank. Other changes in assay conditions, including addition of sucrose, detergent, protease inhibitors, specific activity of ^14^C‐ornithine, the nature of the trapping agent used, and incorporation of a sonication step, did not have a significant effect on ODC quantification (≤20%). Thus, seemingly minor variations in assay conditions can greatly affect the results, which may provide a partial explanation for the variability of ODC activities reported in the literature. Strict quality control measures are mandatory in the interpretation of clinical observations utilizing this marker as an endpoint. © 1992 Wiley‐Liss, Inc.