Spermidine acetylation in N1 and N8 position in rat brain and in N-ethyl-N-nitrosourea-induced gliomas.

N-ethyl-N-nitrosourea-induced rat gliomas showed a stimulation of cytosolic spermidine N-acetyltransferase activity compared with normal brain, with an increased formation of N1 and N8-acetylspermidine, suggesting the activation of two enzymes acetylating the polyamine in N1 and N8 position, respectively. The enhancement in cytosolic spermidine N1-acetyltransferase was probably responsible for an activation of the polyamine interconversion pathway in gliomas, as indicated by an accumulation of N1-acetylspermidine and a marked increase in putrescine. Spermidine N8-acetyltransferase, although acetylating histones at a high rate, seemed distinct from the nuclear enzyme, as, unlike from the latter, it showed very low affinity for putrescine and was not inhibited by methylglyoxal bis(guanylhydrazone).