Magnitude of ornithine decarboxylase induction by epidermal mitogens: effect of the assay technique.

The polyamines, putrescine, spermidine and spermine, as well as ornithine decarboxylase (ODC), the rate-limiting enzyme of polyamine biosynthesis, are increased in the blood, urine and skin of psoriasis patients. A study of the association between stimulated epidermal cell proliferation and induction of ODC activity was done using both an intact, living cell ODC assay and the routinely used homogenized cell supernate assay. 10(-6) to 10(-8) mol/l of the tumor promoter, tetradecanoyl phorbol acetate (TPA), 10(-3) mol/l 8-BrcAMP, 10(-6) mol/l cholera toxin and 10(-3) mol/l MIX, which are epidermal cell mitogens, were used to stimulate basal cells in short-term suspension cultures, freshly plated monolayers, or up to 8-day-old cultures. The results showed that the ODC enzyme must be assayed in supernates from disrupted epidermal cells in order for significant ODC induction by hyperplastic agents to be observed.