Deoxycytidine is salvaged not only into DNA but also into phospholipid precursors II. Ara-C does not inhibit the later process in lymphoid cells

A Novel Effect of the New Antileukemic Drug, 2-Chloro-2′-deoxyadenosine, in Human Lymphocytes

“…Lymphocytes were labeled either from [31-1]dThd or from 5-[3H]dCyd in the presence of increasing concentration of Cl-dAdo (Fig.1 ). In accordance with our previous results [12][13][14][15][16][17][18], incorporation of [3H]dThd into DNA was much higher than the incorporation of [3H]dCyd in tonsillar lymphocytes. In addition to this difference, a more pronounced inhibition of DNA synthesis was found in case of [3H]dThd labeling than in case of 5-[3H]dCyd labeling (Fig.1, DNA).…”

“…Thin layer chromatography (TLC) was used to analyze the nucleotide and liponucleotide fractions, as described earlier [14 Briefly: In case of [3H]dThd labeling, nucleoside monophosphates were separated on PEI cellulose using LiCI for development; In case of [3H]dCyd labeling, chromatography was performed on Kieselgel 60F254 (1st dimension: butanol-acetatewater 2: I: I; 2nd dimension: chloroform-methanol-ammonia 1:1:1) to separate labeled nucleosides, mono-, di-, and triphosphates from dCDP-choline. Results with this method were similar to the separation technique with HPLC used earlier [14]. The ethanol insoluble material was washed with 0.5N perchloric acid twice, and acid insoluble fraction was hydrolyzed and measured for radioactivity (DNA fraction).…”

“…Exogenous dCyd can be used intracellularly for dCTP as well as for dTTP synthesis via deamination of dCMP, methylation of dUMP and its phosphorylation to dTTP. In tonsillar lymphocytes, the conversion of [3H]dCyd to dTTP can exceed 55-70% of the total [3H]dCyd taken up by these cells [13,14], resulting in a low incorporation of 5-[3H]dCyd into DNA, as the radioactive labeling is lost in the methylation step. As it was shown earlier in our laboratory [14], conversion of [11-I]dCyd to dTTP can be inhibited by high concentration of exogenous dThd, leading to an increase of [3H]dCyd incorporation into DNA via the dCTP pathway (see also Fig.2 , inserted table).…”

“…In tonsillar lymphocytes, the conversion of [3H]dCyd to dTTP can exceed 55-70% of the total [3H]dCyd taken up by these cells [13,14], resulting in a low incorporation of 5-[3H]dCyd into DNA, as the radioactive labeling is lost in the methylation step. As it was shown earlier in our laboratory [14], conversion of [11-I]dCyd to dTTP can be inhibited by high concentration of exogenous dThd, leading to an increase of [3H]dCyd incorporation into DNA via the dCTP pathway (see also Fig.2 , inserted table). To investigate weather Cl-dAdo might effect the conversion of dCyd into dTTP, metabolism of [31-1]dCyd was investigated in the presence and absence of non-labeled dThd (Fig.2 ).…”

“…In our laboratory, dCyd was shown to be used not only for DNA but also into phospholipid precursor synthesis in tonsillar lymphocytes [14][15][16][17]. A significant conversion of dCyd into dTTP was also demonstrated [13,14].…”