Rectal mucosal ornithine decarboxylase activity is not a useful marker of risk for colorectal neoplasia.

Rectal mucosal ornithine decarboxylase activity has been reported to distinguish patients with adenomas from normal controls. In order to further explore this association, we assayed biopsy samples from 119 unselected individuals undergoing routine colonoscopic examinations. The overall mean ODC activity was 127.4 (+/- 93.1 SD) pmol/mg protein/hr. There were no differences by age, sex, or race. Tissue handling and storage influenced ODC activity. Specimens collected and transported on Dry Ice had higher ODC activity than specimens initially frozen in a -20 degrees C freezer. After adjusting for storage and collection method, the activity was similar in subjects with adenomas (126.3 pmol/mg/hr) compared to those without adenomas (128.8 pmol/mg/hr). We conclude that variations in assay technique make comparisons between laboratories difficult. Patients with large-bowel adenomas do not necessarily have higher ODC activity in uninvolved rectal mucosa. Further study of the environmental and genetic factors that influence rectal mucosal proliferation may improve our understanding of carcinogenesis in the large bowel.