Polyamine acetylations in normal and neoplastic growth processes

The expression patterns of cytosolic and nuclear polyamine acetyltransferases were studied in normal and neoplastic growth processesin vivo andin vitro to evidentiate the roles played by these enzymes in cell proliferation. In regenerating liver, cytosolic spermidine/spermine N(1)-acetyltransferase showed similar augments of mRNA level and enzymatic activity during the prereplicative period (4-8 h), whereas spermidine N(8)-acetyltransferase activity increased later (24 h) when DNA synthesis was maximally enhanced. In fibroblasts continuously dividing, the messenger for spermidine/spermine N(1)-acetyltransferase rapidly accumulated after serum-stimulation. In cultured Morris hepatoma cells stimulated to logarithmic growth, spermidine N(8)-acetyltransferase activity remained at plateau for 1 day declining thereafter, while spermidine/spermine N(1)-acetyltransferase activity immediately decreased. In Yoshida AH-130 hepatoma cells transplanted in rat peritoneum, spermidine N(8)-acetyltransferase and spermidine/spermine N(1)-acetyltransferase activities rose, respectively, in concomitance with elevated proliferation-rate and quasi-stationary phase of growth. Since the expression of cytosolic and nuclear acetyltransferases underwent different temporal activation, an involvement of these enzymes in separate metabolic processes controlling normal and neoplastic growth may be suggested.