I. - Indagini Sul Metabolismo di Fosforo Nucleinico di Tumori da Trapianto - Inibizione da Tiopirimidine

Our previous researches made evident the inhibiting action of a pyrimidine analogue (2-thio-5-methylcytosine) on the growth of some experimental tumors. Therefore an investigation has been carried out in order to study wheter an inhibition of nucleic acid synthesis is associated with the tumor growth inhibition.

The ARG technique, or stripping technique, has been employed with ³²P as tracer element. The research has been carried out on rats bearing Walker carcinosarcoma and treated with 2-thio-5-methylcytosine.

The employed ARG technique, which shows only the ³²P bound to nucleic acids, allows also a quantitative evaluation of radiophosphorus uptake in those tumor areas showing a more active growth and no necrosis. In addition it gives evidence to the presence, in treated tumors, of areas histologicall unaltered which do not take up radiophosphorus.

In the group of the treated tumors the ³²P uptake was found to be the 17 per cent lower than in the controls, 24 hours already after the drug administration. A further decrease is observed following subsequent administrations. Forty eight hours after the drug injection the values of ³²P uptake show an increase and overcome even those of the controls (+21 per cent). The values of mitotic coefficients parallel those of ³²P uptake. In the intestinal mucosa of the treated animals both ³²P uptake and the mitotic coefficient are found to be unmodified during the treatment and somewhat diminished after it as expression of a cumulative effect of the drug.