title: Uridine as the only alternative to pyrimidine de novo synthesis in rat T lymphocytes.
abstract: Concanavalin A-induced proliferation of rat T-lymphocytes is completely inhibited by 10(-5) M pyrazofurin, a potent inhibitor of pyrimidine de novo synthesis, as judged by cell viability and [3H]thymidine incorporation. Proliferation is completely restored by 5 X 10(-5) M uridine. Cytidine, deoxycytidine, deoxyuridine and thymidine 10 X 10(-5) M each, fail to re-establish proliferation but produce an isotropic dilution of [3H]thymidine uptake in DNA. Bases (cytosine, uracil and thymine) neither restore proliferation nor induce isotopic dilution. The unexpected inability of cytidine to reverse de novo pyrimidine synthesis inhibition suggests a lack of cytidine deaminase activity in rat T-lymphocytes. This is confirmed by a direct sensitive radioisotopic assay (less than 0.001 nmol X min-1 X 10(-6) cells).
mesh_terms: D000577:Amides; D000818:Animals; D003208:Concanavalin A / Q000494:pharmacology; D003564:Cytidine Deaminase / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D003841:Deoxycytidine / Q000378:metabolism; D008213:Lymphocyte Activation; D011720:Pyrazoles; D011743:Pyrimidines / Q000096:biosynthesis* / Q000378:metabolism; D051381:Rats; D012263:Ribonucleosides / Q000494:pharmacology; D012266:Ribose; D013601:T-Lymphocytes / Q000378:metabolism*; D014529:Uridine / Q000096:biosynthesis*
chemical_list: D000577:Amides; D011720:Pyrazoles; D011743:Pyrimidines; D012263:Ribonucleosides; D003841:Deoxycytidine; D003208:Concanavalin A; C002997:pyrazofurin; D012266:Ribose; D004247:DNA; D003564:Cytidine Deaminase; D014529:Uridine