EFFECTS OF RETINOIC ACID AND JUVENILE HORMONE ON INDUCTION OF ORNITHINE DECARBOXYLASE ACTIVITY BY 12-O-TETRADECANOYLPHORBOL-13-ACETATE

  • 1 January 1978
    • journal article
    • research article
    • Vol. 38  (9) , 2896-2899
Abstract
The tumor-promoting agent 12-0-tetradecanoylphorbol-13-acetate (TPA), a highly active comitogen in phytohemagglutinin-treated bovine lymphocytes, induces an 11-fold increase in ornithine decarboxylase [EC 4.1.1.17] activity over cultures treated with the lectin alone. This synergistic action of TPA could be antagonized by the simultaneous addition of the acyclic sesquiterpene, insect juvenile hormone III. Retinoic acid (vitamin A acid), an inhibitor of the tumor-promoting action of TPA in mice, was also an effective antagonist but required administration to lectin-activated lymphocytes 1 h prior to TPA. Apparently metabolic activation of retinoic acid is required to exert its antagonistic action. Comparison of the responses in the lymphocytes and mouse skin suggest that the lymphocytes provide an excellent system for studying the molecular processes through which phorbol esters and retinoids influence the growth and differentiation of normal and premalignant cells.