N1-Acetylspermidine in Cultured Human Lymphocytes

The naturally occurring polyamines, putrescine, spermidine and spermine, have been implicated in many growth processes and in differentiation (Cohen, 1971; Bachrach, 1973; Russell & Durie, 1978). Their concentrations and the activity of their biosynthetic enzymes increase significantly in proliferating cells (Tabor & Tabor, 1976; Janne & Raina, 1968) and neoplastic tissues (Bachrach, 1978; Russell & Durie, 1978). One of the models investigated is the lymphocyte induced to blastogenesis by a lectin. It has been shown that cellular polyamine concentrations increase significantly during the transformation process (Morris, 1978), as do the biosynthetic decarboxylases, i.e. ornithine decarboxylase and S-adenosyl-L-methionine decarboxylase (Fillingame & Morris, 1973; Kay & Lindsay, 1973). Several polyamine-catabolic pathways are reported in the literature. Oxidation of polyamines has been studied extensively and y-aminobutyrate has been isolated as the oxidation product of putrescine (Bachrach, 1973). In addition, there are several lines of evidence suggesting that polyamines undergo acetylation. The mono-acetyl derivative of the diamine putrescine was found in various tissues, including human brain (Perry et al., 1967), and in several organs of other vertebrates (Seiler et al., 1973). N1and N8-Acetylspermidine have been shown to occur in the urine of normal subjects and cancer patients (Abdel-Monem et al., 1975). In the present study we used human lymphocytes, stimulated for transformation, as a model for normal human proliferating cells, and we present evidence that N-acetylputrescine and N1-acetylspermidine are formed in these cells when they are grown in vitro in the presence of [14C]putrescine.