Phorbol esters stimulate spermidine/spermine N1‐acetyltransferase activity in mitogen‐stimulated bovine lymphocytes

Phorbol 12‐myristate‐13‐acetate (PMA) is shown to induce spermidine/spermine N 1‐acetyltransferase, a rate‐limiting enzyme of polyamine biodegradation, in bovine lymphocytes. When PMA and phytohemagglutinin (PHA) were added simultaneously, the enzyme activity was stimulated synergistically. The ability of phorbol esters to stimulate the enzyme activity was consistent with their tumor‐promoting ability. Phorbol, which is not a tumor promotor, was incapable of stimulating the enzyme activity. Phorbol diacetate weakly stimulated the activity of the acetylase. Phorbol dibutyrate had a similar stimulatory effect to PMA. These results suggest that the spermidine/spermine N 1‐acetyltransferase may play an important role in changes in polyamine levels in phorbol ester‐treated cells and that the increase in the enzyme activity may have some relationship to the control of cell growth and differentiation by phorbol esters.