The effects of Prostaglandin (PG) E2 treatment of human T lymphocytes on polyamine metabolism were investigated. PGE2 is known to inhibit lymphocyte proliferation, while polyamines play an important role in several biochemical processes leading to increased cell growth. Preincubation of T lymphocytes with PGE2 (10(-6) M) for 10 min was able to increase ornithine decarboxylase (ODC) activity and putrescine as well as spermine levels, while spermidine concentration was drastically reduced. After 30 and 60 min of treatment, a decrease in ODC activity and putrescine concentration was observed. On the contrary, the initial inhibition of spermine-N1-acetyltransferase (SAT) activity was followed by a progressive increase of this catabolic enzyme. These changes were related to modifications of cAMP concentrations. Our data may help clarify the mechanisms underlying the biphasic effect of PGE2, which ultimately leads to inhibition of cell proliferation.