Abstract
The antitumour activity of some pyrimidine thio-derivatives has been studied simultaneously with their chronic toxic action.
2-thiocytosine (showing a rapid and nearly total urinary elimination), subcutaneously injected to rats in dose of 100 mg/kg for 39 times consecutively, induces only a slight reduction of erythrocytes and leukocytes in the circulating blood, with relative lymphocytopenia and moderate increase in leukocyte fragility, whereas the values of basal metabolism and weight curve are unmodified.
From a morphological standpoint, the only valuable data are a slight stimulus towards neutrophils maturation and a similarly slight lymphoid hyperplasia in the lymph nodes.
2-thio-5-methylcytosine, subcutaneously injected at the same dose for 11 times consecutively, causes a remarkable mortality rate and inhibition of the body growth. Furthermore, differential blood count inversion, increased fragility of withe blood cells and inhibition of the first stages of erythropoiesis with stimulus towards neutrophils maturation are observed.
The morphological changes are mainly characterized by nuclear degenerations of the reticuloendothelial system, which are particularly manifest in the spleen and may lead to cell death and, consequently, to reduction of the cellular density. As concerns the urinary elimination, in this case the 22 per cent only of the administered dose is recovered in urines.
The changes induced by both the experimented pyrimidine derivatives, and especially by 2-thio-5-methylcytosine, are compared with those referred to in the literature concerning antimetabolic products.
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